I want to take this answer in two parts.

First, when do the spells effect redux.

In my experience in the long and slow climb from 55 to 202 spells, the turning point is in the 75-80 spell neighborhood. Below that I felt Menos was very resistant to physical blows. I noticed him getting a little bit squishy by the time I halted at 1635/140. By the time I hit fully 1x in spells, the decline became a near free fall. If you want to maintain some redux/warrior like characteristics than 75 spells or below is going to be your limit.

Secondly, when is it not worth adding additional paladin circle spells.

For me, the answer was 162 ranks. I would have pushed to 182 if not for the utility offered from 125, 130, and 140. As nice as it is to be able to tank a hit, it is twice as nice to incapacitate the critter from guarded and then smash him from impunity. I wouldn't (and did not) go right there post cap. I added dodge to offset the melee attacks, added harness power to make use of the spells more, lore to boost DS/DF/AS. But when I was ready to start the wonderful slog of 90,000 exp per spell, 202 was the final goal.



Sweet is the sound of the pouring rain,
And the stream that falls from the hill to plain.
Better than rain or rippling brook,
Is a mug of beer inside this Took.