With C2P I am not sure what purple hero will turn up next. My view is go with variety and play with what you currently have. So my vote went to Quintus and hope you get the costume.
Good luck
IMHO Quintus is not as bad as a lot of people are calling him. I was close to maxx him but pulled Kunchen on last Atlantis, so placed him on queue again.
I voted save the tabards but I don’t want you to feel pressured into that decision.
If you have coin pulls and happen to get a Kageburado or Ursena (as unlikely as it is) I would rather be able to max them than get caught waiting to level them.
However the truth is you may never draw another dark hero and waiting would look dumb in that case. But I’d rather be hopeful than possibly regret leveling a hero I may not use often.
On the flip side if you use Quintus & Thoth more power to you and game your way.
Totally agree with what you are saying about Quintus. I got him early doors and left him to one side because of all the negative comments. However, I got his costume at the last event so he is max +6 and I am just levelling his costume to get the bonuses
Save your tabards. As everything here is mostly RNG, you may never know which powerful 5 star purple may land on your lap since you are C2P and may have some amount of gems once in a while, not to mentioned that all events have tokens or coins to pull heroes to (keys, atlantis coins, event coins), easily obtainable from quests or the event itself. However, if you happen to get your tabard count to at least 11, go ascend Quintus. The view that you level available heroes in your roster or the best hero is the one that you have, in my honest opinion, are only mostly applicable to F2P players where they barely summon at the portals compared to C2P and P2W players. C2P and P2W players, by reason that they have more gems than F2P players, have more chances of summoning ideal heroes. I suggest you build up more of your purple 4 stars, i.e. Rigard, Proteus, Tiburtus, Cheshire Cat, Ammeona, and some of their dupes.
I try to be an optimist but, as an owner of a maxed Quintus, he does about as much damage as a sniper…at slow speed. With Kunchen and his costume (I am lucky enough to have both), he has a little more smacking power but not much. I would either burn some Atlantis coins in March for Aeron and Ursena or May for Kage and May HOTM (if it’s a good one).