I've got a pet that heals about 30, on a wizard with 25 def, para def or para hp ring?

If your def is maxed I find it's always best to go with an HP ring.
And with a ranged class you shouldn't be taking lots of damage anyway so HP is definitely your best bet.

This.

I always take hp ring (nowadays I like to use expo tho..)

But usually HP ring whatever class I play. I feel better about that ~+120-180 hp than few def..

If you don't have max def, then it's up to you ofc.