Unique gym defender dilemma

I'm looking for another "project" to keep me interested in PoGo. I had been working on a number of rare guys to put in gyms but since the latest nerfs I've been bummed out.

So here is my question - Which guy do I focus on and have as my buddy to acquire more candies?

I have a 100% (hatched bulbasaur that I evolved into an) Ivysaur. I only need 13 more candies for my first Venusaur. As it is only level 20 and bulbasaurs are extremely rare here it will take some time to power it up to level 30. But it would be a very rare gym defender here. Not many around at all. Anyone know how it holds up in gyms now-a-days? (understanding that gyms rarely go above level 4-5 since the latest changes).

The other project is my 96% Muk (15atk-15sta-13def). His CP is 1732 as I have powered him up a few times. I think he's about level 23-24 right now. I've only ever battled one high level Muk (was about 2200CP) and he did cause me a bit of trouble until I figured him out. My Muk has Poison Jab and Dark Pulse which this site says is the best defending move set. Anyone comment on how good it actually is?

I'm super bummed out with the nerfs to Blastoise, Vileplume and Slowbro. I worked hard on maxing those guys out as they are extremely rare here and were not too bad to put in gyms as their CP was decent before the nerfs (all were 2100+ for me).