There are 100+ champs with this issue on dragon, lol.  Kind of like only fixing CH for FK.  I find the AI more annoying on the Magma dragon in DT.  

Yeah fair enough, just noticed that Rhazin uses his A3 as well. I guess the bottom line is that they didn't code the AI properly vs Dragon's immunity to TM control. Wonder if it's maybe because originally it wasn't immune? As the tooltips still don't actually say he is.

Always was immune as far as I recall.  To be fair, I am guessing there was never any differential AI for waves and bosses.  We can say fixing champ xyz for the dragon is simple, one line of code, but in reality it is bigger than that.  Unfortunately I don't think the 2022 user AI control will even fix this issue as I don't we will be able to have Rhazin use A3 on waves but not Dragon.  Some champs have TM reducing skills that do other things as well so its not as simple as do not use any TM reducing skill on dragon.

True enough, but they seem to have figured it out for CB - although my guess is the solution they derived was custom code for each champ in question :/

In  each  dungeon,  the  bosses  are  weaker  in  lower  stages.

the  fire  knight  has  less  shield

the  ice  golem  has  less  points  where  he  counterattacks

each  of  the  keeps  skills  are  weaker

The  dragon  might  have  been  susceptible  to  turn  meter  control  in  the  lower  stages.