I've hit zelemir 1 with as much as 4 minutes ahead of my time when I achieved that 56 minute run. Of that, I managed to carry 2 of those minutes ahead to the end but had a really rocky last couple fights (Zelemir's Army, Zelemir 2 went poorly, ended with 55:47.)
Cracking the 50 minute barrier seems like it will be doable with current strats, but I'll have to be a lot more confident about setups in the later levels - which is difficult, because the last two non-boss levels (archerless and zelemir's army) require some precision timing on Azra's spell usage or else the flipping MACH 5 slugs leak when the monstrosities pop.
More than that will be really difficult.
I think a robot could break 40 minutes, maybe even 30, since there's a huge amount of time that can be saved simply with instant unit management and menuing. I wonder if there's a way to TAS the game...