Remove skill tiers
Firstly, let me state the only reason you had the “oh neat, lets try it” attitude in the beta was because things were new. Of course after your fifth character things aren’t going to be as exciting anymore.
And also, It sounds like now you know exactly what you want and its all t3, so opening everything up again would not magically make you want to experiment, it would just cost you less skill points to get what you want. This kinda sounds like you just want to save a few skill points by not spending them except on the very specific ones you somehow already know you want (or are you just assuming t1 and 2 skills are crap?).
I think you need to try to force yourself to give new abilities a try instead of finding a few you like and not changing.