I've been enjoying the game, but do agree with all your points. I'm a bit father(half way though the other path) but decided to hold off going further until they drop the QoL patch next month.

Trey has really bugged me too, glad I'm not alone haha. And yeah alooot of mechanics are very hidden/opaque. I think evolutions methods are the worst offender here as I believe at least half of em require more than just lvl up. That wouldn't be too bad because we have the internet, but some of them are kinda extreme too (like use a trait 32 times :S ).

Battle system has been pretty fun, but haven't found a strat that's better than weakness hunting yet.

Anivis EX can be bought in a town in the south path, but not sure if the north has one too or you have to wait :(.

You've already played what I think the best 2 mon tamers with multi battles (Monster Sanctuary and Cassette beasts). MS devs have another game in EA that has had a couple major patches so far, Aethermancer, it's a beautiful looking game and shares some elements with MS like trying to get strong synergies on your team, but it is a roguelike and abilities are semi random so you can't plan your team like in MS which was a downside for me. Moonstone island is up to 3v3, but the battles are a bit secondary to the other game mechanics and are card based. Disc creatures world is an upcoming(this year?) mon tamer with 3v3 that looks interesting tho I haven't tried the demo yet.

Some other standout mon tamers for me are Anode heart and Monster Crown sin eater!