I have all 3. Wu and Tarlak maxed and Miki at 3.33 currently. One advantage that Tarlak and Wu both have is that they have high tile damage regardless of their special. So depending on who you have, it makes sense to have them in your green and yellow stacks regardless.
So on purple titans, I run Miki/Wu/Chao/Joon/Li Xue. (don’t have another compelling yellow) I don’t use Wu’s special unless Miki dies or if Wu is charged, Miki isn’t (and no blues are on the board) and there are a lot of yellow combos to be had.
On blue titans, I’m experimenting with Miki/Tarlak/Hansel/Caedmon/Buddy or Melendor. Since their specials overwrite each other and you don’t have any accuracy issues like with Wu, you can have one of their specials running almost the whole time you’re fighting with using just a few minor mana potions to help out. Even if you don’t use Tarlaks special, his 824 attack is stellar.
But it really just depends on your bench and who else you have. For me, I have no other compelling blue projects so I’ll take Miki to 3.70 b/c I have only 3 telescopes at the moment.