Im probably not the only one who got completely stuck on this level. I can#t advance at all, and its just a war of attrition guarding bridges until I eventually run out of gold and have no choice but to advance. The humans have clerics, and as soon as they are nearby ALL of their units becomes imortal, due to them healing them quiter then I even manage to make a dent. Do anyone know how to counter them7 Raising skeletons only work for scouting, essentially. And the spearmen works great for defence. But I have no means at all to attack due to the clerics. I can only move four units at most, and I have to select them individually, which means selecting other units takes a long time. And everything is immortal as soon as they are close to the clerics.

There is Mouse Helper workingsimilar to trainers.
Just in case you can drag over 4 units to select (but no hotkeys for groups yep). Like Ctrl+mouse or something.

clerics should get out of mana... they cant do it forever, right?

Go south - You'll encounter another mine.
Then go east - there will be path that leads to human camp from the south. It have fewer defenders, and when you'll start to smashing their buildings, footmans will come defend and clerics probably will not.
That should solve your problem.

i know im late i supposse you figured out, one thing i like to do when the ai is abusing heals is leveling my spear orcs up to tier 3, because 5 or 6 of those orcs will destroy any unit no matter the healing if all else fails...ABUSE CATAPULTS