“It is a point of great delicacy, and you must assist us in our endeavours to choose exactly the right line of conduct.” (1)

I agree Sir Thomas has relied too much on Mrs. Norris—she is involved from writing letters to educating his daughters and escorting them in society and he has though out never relied on Lady Bertram in the slightest. Before going to Antigua he specifically considers his wife deficiencies:

He could not think Lady Bertram quite equal to supply his place with them, or rather, to perform what should have been her own; but, in Mrs. Norris’s watchful attention, and in Edmund’s judgment, he had sufficient confidence to make him go without fears for their conduct. (3)

It is interesting he relies on her watchful attention rather than judgment. After his return from Antigua Sir Thomas is:

Sir Thomas gave up the point, foiled by her evasions, disarmed by her flattery; and was obliged to rest satisfied with the conviction that where the present pleasure of those she loved was at stake, her kindness did sometimes overpower her judgment. (20)