He is very easy to upgrade stars and you can usually get him sainted a lot easier that Cianna and at a tenth of the cost. I usually get multiple cards so I have 90-100% chance of upgrading him. (Over the past year that I have played anything less than 90% chance of success, is like 99% chance of failure - I have lost at least 5 leader cards w/90% chance of success across multiple servers, as well as probably 5000+ gems with the gem insurance just on the failures from "70-90%" chance of success. Good luck trying that with Cianna it takes a long time and tons of Credits just to get each Cianna card and usually you get about 8000-10000 from CW and it cost 5000 per card .

Downside is that Thuc has an upper limit (I think it is Angel 5 and can't go higher)

But stars cost less, and you have a way higher chance of success on your attempts with Thuc than with Cianna.

While he starts weaker and has a lower upper end, he can more quickly and easily exceed Cianna and stay that way while you spend a lot of time trying to upgrade her

Generally I only use these 2 toons in Cerb/Baal and then take them out for more useful characters.

A single stun attack against a single enemy like Baal/Cerb gains you as much as 4 additional attacks against the one.

But when having to fight 5 enemies the multi attacks of Adamanti, Rhize, Dawnbringer, Valla, Smoulder, etc. outweighs any "potential" stun chance.