As a humble, mostly-lurking observer who's interested in titans and game design (and who wouldn't be!
), I think @Blip is right about the difficulties with titans in a game like Epic Armageddon. Anything that is hard to kill and doesn't degrade with damage, plus has nasty weapons, will be very difficult to balance. Large point values are more easily balanced because you have more granular effects from taking out individual titans (and so large, titan-focussed battles probably do quite well, especially with less models to take care of!).
EA also has the aforementioned issue that the number of units is both critical for wining games and for making games interesting; individual units are just not complex enough to make smaller (number of formations-wise) battles interesting (unlike previous versions of titan rules or, say, Battlefleet Gothic).
Since you don't get many titans in other lists, these unbalancing effects are pretty small for most armies but I think if EA had continued with support, GW would have revised multi-damage capacity unit rules to give those units more detail and micromanagement or, at the very least, granular damage results. Both as much as I'd like it and as much as it might improve the game, I think revising titan rules like this is a very big task since it should be applied to all titans throughout the game.
So, that leaves small changes! I actually quite like that plasma generator rule, @Vaaish! Though I've never quite been able to get a DC-linked generator system to work out for the existing superheavies and their weapons (and, potentially, movement speed, repairs, and shield charging). Perhaps replacing the initiative system for titans only with a generator system would do it? Instead of passing initiative tests for orders, you'd use plasma generator points to do those orders (more power to legs but none left for shooting ~= March, for example). This would stop you from having your giant point-sink fail initiative tests and flounder around, too, whilst mitigating their abilities in a similar way to activation.
Perhaps the easier option is removing the automatic Fearless. I would propose instead that they get a new rule that allows suppression by blast markers but none of the other penalties of non-Fearless units (so no Breaking and automatic damage from shooting; but not sure about other penalties to initiative). Using blast markers to represent superficial damage that gets repaired lets you wear down the effectiveness of titans by taking positive action against them and is easy to implement. You could use some justification about veteran Princeps being sent with ally-titans as suggested earlier to make up for the discrepancy if there were no game-wise changes.
Anyways, these are just food for thought, and maybe something interesting to try out in friendly games! I apologise for the large amount of text but my dream of an integrated infantry-vehicle-interesting titan game just won't die!
Well done to Vaaish and everyone else who's contributed to the AMTL list as it stands, too, it's made for interesting reading and it's a testament to the skill required to address a very challenging limitation of the core rules without changing anything fundamental.