You can use your den quest from there if need be. Level 45-50 would allow you to put enough points in your skill tree to give everything a thorough test. I don’t see a problem having endless respecs until a certain level so you can test all the abilities to your heart’s content. What if you don’t like this new play style going forward? Time to start over. It takes a lot of time for a new/casual player to get this far only to “test” things out to see if they like the play style. Unlock a new ability at 18? Oh wait, you can’t test it because you’re going up another tree. Some of these play quite a bit different than you had previously. Most guides start with a basic build to follow and then respec 25-35 when you can finally unlock end of tree abilities.
