Beat it on my 2nd attempt. But after a while you just straight up run out of things to use blue crystals for, at least things that matter. Half the spells basically do nothing (1 dps poison vs 1k hp enemies, wow so useful). When you start getting the immune waves it just gets annoying, since you can't really get enough tower saturation near the base of both types. So I just ran 3x magic towers near the base for their high attack speed with 2x freeze runes on all of them, except one with 1x insta kill, to permafreeze enemies and let the 5% chance to insta kill eventually kill all of them.
As far as I can tell most runes are bugged though, pretty sure my stone towers never triggered any rune ever. Never saw poison rune trigger on any tower either, or slow. The only rune combinations that I 100% saw work was freeze on Magic Tower and insta kill on Magic Tower.