Tyranitar 96IV IT/FB
I levelled up my 96% IV Tyranitar with Iron Tail/ Fire Blast to level 31 at 3184 CP. I now have 51 candy from catching and hatching a few more larvitars. I know this moveset gets a lot of hate but I'm actually quite happy using this moveset for attacking gyms. Iron tail does decent damage against many mons and outclasses bite on defense. Not to mention its high IV and high max CP potential is competitive enough that it can usually make the top 5 in most gyms (in the current gym meta). Furthermore, I'm absolutely certain that moves will be reworked again in the future rendering previously good moves like psycho cut and zen headbutt to sub optimal.
So taking these into account, should I continue powering this bad boy up or just wait and evolve another tyranitar?
Answers
I'd power up to use in gyms now...other than that, I'm of the mindset that having STAB is better simply BECAUSE of moveset changes and having STAB means it "should" normally do more damage than a non-stab move.
For most legit (non-spoofer) players, you're not going to have tons of 96% Tyranitars due to needing 125 candies alone to evolve and more to powerup so given what rolled (bad moves) and T-rex simply having high CP means you have to power it up.
This is similar to my Blissey comments of how many can people really afford to keep evolving hoping for better movesets? Better to power up fewer higher Blisseys than get 4 or 5 lower level (useless to stay in high CP gyms Blissey just to show you have one).
If Tyranitar's maxed CP was only 2000, then I think no one would bother honestly.
TL:DR - Power up to get max CP, that's it...moveset matters little from a DPS perspective when it's defending a gym since a determined (or high level) attacker will simply tear the gym down...yes, he may use more potions, but any high level player worth their salt isn't worried about running out...and play too much anyways.
It seems like its cp is high enough for top5 spots. So why should you bother to power it up even more? In my experience, if more than the last three pokemon in a gym are taken out, then the whole gym is going to be defeated anyway and then it doesn't matter at all whether you held spot 4 or 1...
Only exception might be if a gym is consistent for months and time by time a second account bad ass comes by and wipes the last one out. The sixth one might be a problem for you then...
As an attacker I often read that most people tend to power up only until Lvl30. To me it seems like you T-Rex is already strong enough. But in fact I have not much experience with that since I'm only Lvl28 :D