I hope this is the right place for this question, if not, i'm sry moderators but i missed the post. I was playing a quest where 3 heroes wanted to guard against the same monster on the overlords turn. We have all guarded and are all in range and by the rules we should all be able to guard, but it seems overpowered that all of us can guard against the same monster. Can we all guard against the same monster or do only one of us get a guard roll per monster?

You dont actually "guard" against a particular monster, you just "guard".

Each hero on guard may interrupt the overlords turn (at any time).

So for example, one monster might decide to move and attack - one hero on guard might interrupt. If they dont kill it, the next hero can interrupt, and so on. This uses up their guard order.

Also not, that the guard order can be used at any time in the OL's turn, not just when the OL moves a monster. So, the OL cant be clever and say "well, I'm not moving anything", because then just before the OL's turn ends, the heroes can activate their guard orders, and those with ranged / magic attacks can interrupt and attack anything they can currently see.

Guard order is very powerful. In our last campaign, virtually every hero turn consisted of going on guard.