Depending on what you get powerwise, I'd almost recommend at least some recovery due to some high end per second costs.
50s: Yumi Eryuha-Arch/Energy, Mirria-Thugs/Dark, Meyami Kitsuna-Claws/SR, Celesta Seusen-SS/Invuln, Lady Mirriella-Illusion/Empathy
Arc 503982 "Dimension Xi Epsilon 22-10" Part one of a multi-part arc.
It's possible to build up impressive amounts of s/l/e and/or range defense on a Sonic. While doing so, you'll build up sufficient recovery bonuses. While you're right that high recharge isn't going to transform a sonic/ def, it does help to a degree so throw in LOTGs when you can.
Global = Hedgefund (or some derivation thereof)
You will find that Liquefy never seems to recharge quick enough... well, it never does for me anyway. That would be the only real reason for big recharges other than your attack chain.
Come to think of it you might want to invest in hover for that reason alone. You don't want to be kbing out of liquefy.
I'm playing Sonic/ for the first time and I'm not sure what I should IO for. It doesn't seem like there are any recharge-heavy powers and I'm not too concerned about damage from the secondary because of the -res, so would slotting for Def be the best option? Recovery?