Tiadrin isn't the strongest 10$ hero you can get no, but she is one of the better ones anything she gets fielded on makes it better I have a tiadrin that I fed all the mag/command to and she soloes silver armies very very easily and keep in mind I only spent 11$ on the server I've never bought anything else other than patron and her she just makes life a lot more easier and if you really wanted to you can feed her every stat and get some effect out of everything. When you get her maxxed in all her stats with her shield she has 35/35/35/34 for stats making it extremely easy to craft any item in the game that you want it just comes down to getting the stones to be able to craft everything.
Honestly I thought she was going to be worse than she actually was but after playing with her she is purely automatic and requires no imputs and thats her greatest asset sure she has some "counters" in duels and overall you are better off with jacques but even her counters aren't that bad unless its elena aura + vega favor. Though admittedly i play her with lich so that may have something to do with it but another bonus is she confuses the hell out of priest AI causing them to heal everything but the front which makes your spiders do more damage and also during favor helps push through her heals. That aside she has the best auto trigger ability in the game glory hammer. Besides that she can carry you through the void pretty decently as well during my time with her on 100 she's probably one of the most underrated heroes in the game but in my opinion is one of the strongest but I am in no way saying she is the best she has her issues causing her to stay away from that spot but she is no way "trash" tier even if you dont invest in her heavily just due to her passive abilities.
PS Gazul aura + tiadrin aura in duels makes every archer in the game run if they do not open vega favor it essentially deletes them from the duel if shes stacked.