Lvl 148 Viper at Guardian Captains of Regret HD

Err that xD
I don't use transform at all, it's free haste but doesn't let me use Drain... and I use drain a lot XD

You won't be using drain much at higher levels, assuming you use it for damage. If you just simply want to heal your HP, one drain should do it, or a drain -> DSB -> drain can also work if you're in transform. Overall, using transformation is useful for mobility purposes.

Are there any higher leveled Bucs out there that transform and use a Snatch/DS combo? If so, how is it compared to what we see here? :O

No, not really. I never use snatch, it's quite possibly the most useless 4th job skill. It doesn't reach any further than demolition, DS hits further so you have no reason to drag the monster towards you. It's best replaced with CSB or BSB.