Yes...1) DC goes uup
Which can be a bit of a drawback when you want that 4th 8th level spell.2) About equal to a FvS
DC doesn't matter if you can't break their SR.3) Can't argue here
This is just looney. A Cleric going from 18-20 gets 195 SP. +2 Wis at level 18 (not 20, you have 2 levels of monk) gives 27 SP. That's a major drop-off.4) Fairly irrelevant as the wis increase will offset some of it.
And that same single solitary point is needed in your SR, where you're losing 2 points.Normally, I'd agree with you, but in the game where every single solitary point of DC must be wrenched out, that 1 point can be a significant increase.