@Suicide_Bunny, I wanted to chime in on this as a long-time Mitsuko user, but didn’t have time a few days ago. Mine is +9. I may go further if she starts struggling to survive, but she’s very robust right now.
Emblem Path
I went Def/HP, but actually had a decision at the 8/9 fork. One way is healing and defense, the other is crit and attack. I wanted the defense boost, but regard the healing as virtually worthless. Ultimately, I went crit attack there since Mitusko’s attack is credible, I didn’t mind boosting it, and it struck me as a better value than eating the healing bonus for essentially no return. Another viable solution may be to stop at +7, honestly, especially since you have other valuable sorcerers. Anyway, if you want to read more, here’s the thread where it was discussed.
Usage
Mitsuko is critical in many of my raids against blues in positions other than tank. She excels as part of a stack or as a standalone in a 3/1/1. Plus, something I’m looking at (but giving you an exclusive preview!); I think she may be invaluable in beating Kunchen tanks.
I’m not using her on green titans, nor trying to leverage the reflect against blues.
I don’t use her on defense, but I think she’s a decent tank. Just I’d rather send Gravemaker out as my red hero. She’s not terrible in other spots, but it sounds like you have other better options.
Obviously she’ll be good in some tournament rules, especially the current one where everyone is packing blue hitters into their defense.
Reflect
It’s amazing, but can take some getting used to. The timing can be tricky; I know of at least one poster on the forums who has discussed having some problems getting it right. She’s probably been the third hardest hero for me to figure out, behind Wilbur and Onatel (don’t laugh - I can’t explain why I just could NOT get Wilbur right…I know it’s lame, but we all have some game aspects we struggle with).
She is great at killing average or slower flanks and wings, especially A3E attackers like Frida or Thorne. And of course she’s amazing against Isarnia. A fast flank is more of a toss-up. And even if you’re in time, Magni and Alice often won’t kill themselves. Be prepared to follow up. And be aware that Magni still puts his shield up. I do not automatically bring her against a fast blue flank (where I often do against an average or slower flank/wing).
Lastly, some of the heroes you’ll want to reflect have Pierce: Athena, Alasie, and Finley are still very dangerous. Alasie is particularly troublesome on the flank (significantly less so on the wing), between the chances she fires first and/or Pierces. I still bring her in a lot of those situations, but it’s far from a lock that you get the desired performance.