Which defender should I power up next?

I'm level 27 and looking to build a squad of 10+ solid gym defenders. I have three 'mons already maxed out:

• a Dragonite with dragon breath/hyper beam, who I use as my go-to attacker/trainer
• an Exeggutor with zen headbutt/solar beam
• a Vaporeon with water gun/water pulse

So with those three in mind, I need help picking who to boost next. In order of current level, the ones who jump out at me are:

• a Slowpoke who is very very high level, but may or may not get good moves when I evolve it (and also could be saved for Slowking in gen2)
• a Venusaur with razor leaf/sludge bomb
• a Slowbro with confusion/ice beam
• a Slowbro with water gun/psychic
• another Exeggutor with zen headbutt/solar beam, who has 56% IVs (everything else is 82.2+%)
• an Exeggcute who has 84.4% IVs, but may or may not get good moves and will eat 50 of my 63 candy to evolve

I'm leaning towards the Venusaur, but my brain is still burnt out from farming the event like a maniac, so I wanted to double-check.