I agree. I don't mind niche-crossover. The last thing you want is for only one class to be able to do a thing that's needed, or someone "has" to play it. However, like you say, the "best" should probably remain the best. The mystic went too far, but that was part of UA playtesting. A part I think they should be careful about (sometimes I expect people will downvote a playtest thing because if it's "power level" - the thing they say they will fix later - and you throw the baby out with the bathwater.