Exeggutor with legacy moveset c/seedB for defense
There has been some discussion about Exeggutor and his legacy moves already but mostly about C/soB.
Eggs are not too common around here (also I'm a rather casual player) so I've only been able to evolve one Exeggutor with C/seedB. I never powered him up because I wasn't too happy with the moveset and also didn't have enough candy to get him to a reasonable CP range.
I do have another good eggecute and am patient enough to save up for another evolution but this legacy moveset might be better than all currently available. Is that right?
I don't have a Blissey, Snorlax or Dragonite, my poor Lapras got nerfed so I am desperately in need for some quality defenders.
The Exeggutor is lvl 20 with 84% IVs I believe. I am lvl 29 just about to level up.

Answers
For gym defending, I think it's really hard to use anything other than the top 7 due to CP gym rankings.
Of course, this ALL depends on your gym scene, but for me, you'd need to be level 34+ or so before the lower CP mons will work. A perfect Eggs would be over 2700 CP and maybe near the bottom/middle. There are just too many Dragonites/Snorlax/Rhydons (and now, Tyranitars/Blisseys) to compete with them at the lower levels...
I'd hold off on powering up and save the dust (200k isn't a lot) for now.
C/SeB was almost the best defensive moveset (just behind C/P but close) before the update. Now that Psychic has been nerfed and Seed Bomb buffed, I'd not be surprised if it's ranked best (3 bar move) even if SoB hits like a truck. Anyway, C/SeB and C/SoB are clearly the best defensive movesets for Exeggutor.