You still get Sicken even on made save with Destructive so it would be a nice effect if CLs weren't so high on the Dispel itself. Very difficult to reliably Dispel anything without Mythic Path helping.
It's not too bad now that you can get +3 CL from the DLC robe - any level 20 caster can reach a CL of 26 on greater dispel, which is enough to remove Areelu's buffs with a few casts.
As for raising DC, it's pretty easy if you abuse Expanded Arsenal; if you don't take that option, you need to pick schools and spell types that are well-supported by gear. There's quite a lot of stuff to support Enchantment and Illusion and a decent amount of stuff for certain kinds of evocations, but Conjuration, Transmutation, Abjuration, and Necromancy get kind of stiffed.