Como se livrar da varredura de índice clusterizado?

Eu tenho uma consulta que foi gerada pelo código C#/Linq-To-Entities. Tal como acontece com este tipo de consulta, parece muito feio e duvido que ajude a incluí-lo aqui. Mas eu o executei por meio de um criador de perfil de consulta e descobri que 50,5% do tempo de processamento está acontecendo em uma etapa "Nested Loops (Inner Join)", que está juntando uma busca de índice clusterizado em a2_AssessmentQuestion(0,3%) e uma varredura de índice clusterizado em mesma tabela (13,1%).

Confesso que não entendi bem o que essa "junção de loops aninhados" está fazendo, mas por que a consulta estaria fazendo uma varredura na tabela logo após fazer uma busca de índice, quando os campos que ela está procurando estão disponíveis diretamente por outro índice em exatamente os campos obrigatórios? E sim, eu corri update statistics a2_AssessmentQuestion, sem efeito.

Não sendo um especialista em entender o plano de consulta, agradeceria se você pudesse me estimular para obter respostas para perguntas relevantes; Talvez eu simplesmente não saiba o suficiente para fornecer a você informações úteis suficientes.

Obrigado!

EDIT: FWIW, aqui está a consulta:

SELECT 
[Project6].[ID] AS [ID], 
[Project6].[ID2] AS [ID1], 
[Project6].[ID1] AS [ID2], 
[Project6].[ID3] AS [ID3], 
[Project6].[ID5] AS [ID4], 
[Project6].[ID7] AS [ID5], 
[Project6].[ID6] AS [ID6], 
[Project6].[ID8] AS [ID7], 
[Project6].[ID9] AS [ID8], 
[Project6].[ID11] AS [ID9], 
[Project6].[ID10] AS [ID10], 
[Project6].[ID12] AS [ID11], 
[Project6].[ID13] AS [ID12], 
[Project6].[Number] AS [Number], 
[Project6].[ScholarAssessmentID] AS [ScholarAssessmentID], 
[Project6].[C1] AS [C1], 
[Project6].[GradingStyle] AS [GradingStyle], 
[Project6].[PartID] AS [PartID], 
[Project6].[C2] AS [C2], 
[Project6].[ID4] AS [ID13], 
[Project6].[Description] AS [Description], 
[Project6].[Version] AS [Version], 
[Project6].[DifficultyLevel] AS [DifficultyLevel], 
[Project6].[AssessmentQuestionID] AS [AssessmentQuestionID], 
[Project6].[GradingDueDate] AS [GradingDueDate], 
[Project6].[C3] AS [C3], 
[Project6].[AssessmentFormat] AS [AssessmentFormat], 
[Project6].[C4] AS [C4], 
[Project6].[Structure] AS [Structure], 
[Project6].[Title] AS [Title], 
[Project6].[C5] AS [C5], 
[Project6].[AssessmentFormat1] AS [AssessmentFormat1], 
[Project6].[C6] AS [C6], 
[Project6].[Label] AS [Label]
FROM ( SELECT 
    [Extent1].[ID] AS [ID], 
    [Extent1].[ScholarAssessmentID] AS [ScholarAssessmentID], 
    [Extent1].[AssessmentQuestionID] AS [AssessmentQuestionID], 
    [Join1].[ID1] AS [ID1], 
    [Join1].[ID2] AS [ID2], 
    [Extent4].[ID] AS [ID3], 
    [Extent4].[PartID] AS [PartID], 
    [Extent4].[Number] AS [Number], 
    [Extent4].[DifficultyLevel] AS [DifficultyLevel], 
    [Extent4].[Structure] AS [Structure], 
    [Extent4].[GradingStyle] AS [GradingStyle], 
    [Extent5].[ID] AS [ID4], 
    [Extent5].[Description] AS [Description], 
    [Extent5].[Version] AS [Version], 
    [Extent6].[ID] AS [ID5], 
    [Extent6].[GradingDueDate] AS [GradingDueDate], 
    [Extent6].[Title] AS [Title], 
    [Join6].[ID3] AS [ID6], 
    [Join6].[ID4] AS [ID7], 
    [Extent9].[ID] AS [ID8], 
    [Extent10].[ID] AS [ID9], 
    [Extent10].[AssessmentFormat] AS [AssessmentFormat], 
    [Join10].[ID5] AS [ID10], 
    [Join10].[ID6] AS [ID11], 
    [Extent13].[ID] AS [ID12], 
    [Extent14].[ID] AS [ID13], 
    [Extent14].[AssessmentFormat] AS [AssessmentFormat1], 
     CAST( [Extent4].[Points] AS bigint) AS [C1], 
     CAST( [Extent1].[PointsAwarded] AS decimal(19,0)) AS [C2], 
     CAST( [Extent6].[DueDate] AS datetime2) AS [C3], 
     CAST( [Extent4].[Number] AS bigint) AS [C4], 
    [Join14].[Label] AS [Label], 
    CASE WHEN ([Extent4].[RubricWeight] IS NOT NULL) THEN  CAST( [Extent4].[RubricWeight] AS int) ELSE 0 END AS [C5], 
    CASE WHEN ([Join14].[ScholarAssessmentAnswerID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C6]
    FROM            [dbo].[a2_ScholarAssessmentAnswer] AS [Extent1]
    INNER JOIN  (SELECT [Extent2].[ID] AS [ID1], [Extent2].[AssessmentID] AS [AssessmentID], [Extent3].[ID] AS [ID2]
        FROM  [dbo].[a2_ScholarAssessment] AS [Extent2]
        LEFT OUTER JOIN [dbo].[a2_ScholarFNPAssessment] AS [Extent3] ON [Extent2].[ID] = [Extent3].[ID] ) AS [Join1] ON [Extent1].[ScholarAssessmentID] = [Join1].[ID1]
    INNER JOIN [dbo].[a2_AssessmentQuestion] AS [Extent4] ON [Extent1].[AssessmentQuestionID] = [Extent4].[ID]
    LEFT OUTER JOIN [dbo].[a2_AssessmentQuestionType] AS [Extent5] ON [Extent4].[QuestionTypeID] = [Extent5].[ID]
    INNER JOIN [dbo].[a2_AssessmentPart] AS [Extent6] ON [Extent4].[PartID] = [Extent6].[ID]
    INNER JOIN  (SELECT [Extent7].[ID] AS [ID3], [Extent7].[AssessmentID] AS [AssessmentID], [Extent8].[ID] AS [ID4]
        FROM  [dbo].[a2_ScholarAssessment] AS [Extent7]
        LEFT OUTER JOIN [dbo].[a2_ScholarFNPAssessment] AS [Extent8] ON [Extent7].[ID] = [Extent8].[ID] ) AS [Join6] ON [Extent1].[ScholarAssessmentID] = [Join6].[ID3]
    INNER JOIN [dbo].[a2_Assessment] AS [Extent9] ON [Join6].[AssessmentID] = [Extent9].[ID]
    LEFT OUTER JOIN [dbo].[a2_AssessmentType] AS [Extent10] ON [Extent9].[AssessmentTypeID] = [Extent10].[ID]
    INNER JOIN  (SELECT [Extent11].[ID] AS [ID5], [Extent11].[AssessmentID] AS [AssessmentID], [Extent12].[ID] AS [ID6]
        FROM  [dbo].[a2_ScholarAssessment] AS [Extent11]
        LEFT OUTER JOIN [dbo].[a2_ScholarFNPAssessment] AS [Extent12] ON [Extent11].[ID] = [Extent12].[ID] ) AS [Join10] ON [Extent1].[ScholarAssessmentID] = [Join10].[ID5]
    INNER JOIN [dbo].[a2_Assessment] AS [Extent13] ON [Join10].[AssessmentID] = [Extent13].[ID]
    LEFT OUTER JOIN [dbo].[a2_AssessmentType] AS [Extent14] ON [Extent13].[AssessmentTypeID] = [Extent14].[ID]
    LEFT OUTER JOIN  (SELECT [Extent15].[ScholarAssessmentAnswerID] AS [ScholarAssessmentAnswerID], [Extent16].[Label] AS [Label]
        FROM  [dbo].[a2_ScholarAssessmentAnswerSelection] AS [Extent15]
        INNER JOIN [dbo].[a2_AssessmentAnswers] AS [Extent16] ON [Extent15].[AssessmentAnswerID] = [Extent16].[ID] ) AS [Join14] ON [Extent1].[ID] = [Join14].[ScholarAssessmentAnswerID]
    WHERE (1538 = [Join1].[AssessmentID]) AND ( NOT EXISTS (SELECT 
        1 AS [C1]
        FROM ( SELECT 
            [Extent18].[ID] AS [ID]
            FROM  [dbo].[a2_AssessmentQuestion] AS [Extent17]
            INNER JOIN [dbo].[a2_AssessmentQuestion] AS [Extent18] ON [Extent17].[PartID] = [Extent18].[PartID]
            WHERE [Extent1].[AssessmentQuestionID] = [Extent17].[ID]
        )  AS [Project1]
        WHERE ( NOT EXISTS (SELECT 
            1 AS [C1]
            FROM [dbo].[a2_ScholarAssessmentAnswer] AS [Extent19]
            WHERE ([Extent1].[ScholarAssessmentID] = [Extent19].[ScholarAssessmentID]) AND ([Extent19].[AssessmentQuestionID] = [Project1].[ID])
        )) OR (CASE WHEN ( EXISTS (SELECT 
            1 AS [C1]
            FROM [dbo].[a2_ScholarAssessmentAnswer] AS [Extent20]
            WHERE ([Extent1].[ScholarAssessmentID] = [Extent20].[ScholarAssessmentID]) AND ([Extent20].[AssessmentQuestionID] = [Project1].[ID])
        )) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT 
            1 AS [C1]
            FROM [dbo].[a2_ScholarAssessmentAnswer] AS [Extent21]
            WHERE ([Extent1].[ScholarAssessmentID] = [Extent21].[ScholarAssessmentID]) AND ([Extent21].[AssessmentQuestionID] = [Project1].[ID])
        )) THEN cast(0 as bit) END IS NULL)
    ))
)  AS [Project6]
ORDER BY [Project6].[ID] ASC, [Project6].[ID2] ASC, [Project6].[ID1] ASC, [Project6].[ID3] ASC, [Project6].[ID5] ASC, [Project6].[ID7] ASC, [Project6].[ID6] ASC, [Project6].[ID8] ASC, [Project6].[ID9] ASC, [Project6].[ID11] ASC, [Project6].[ID10] ASC, [Project6].[ID12] ASC, [Project6].[ID13] ASC, [Project6].[ID4] ASC, [Project6].[C6] ASC

Tentei incluir o plano de execução, mas ultrapassei o limite de 30.000 caracteres.

O mais louco é que estou fornecendo AssessmentID = 1538, que é a informação de limitação mais útil na consulta, mas o plano de execução está ignorando esse fato e verificando quase todas as outras tabelas unidas, apenas filtrando por AssessmentID tipo de como uma reflexão tardia...