Sounds like DOL/DOH were dropping the ball. Also, assuming you have at least 2 whm's in the party, if your front line archer gets to 30-40% (depends on how hard he's getting hit), tell the other WHM/party 'archer getting low help' If the 'red' pots are down, (DOL job) the archers get hit HARD...it doesn't take much in this case if a lot of mobs are nailing an archer/cart for them to get in trouble.

Also minor thing, if a cart is going down hard, don't regen at first.(regen just isn't gonna save them if they are going down fast, they need a hp buffer first for regen to help) Cura/Cure Spam AS FAST as possible and try to get other whm to help (most of the mobs are on the cart so you should both be able to help). When you get cart stable and/or at least
35%hp's then regen...cura then if okay protect. That should smooth things out.

It does sound like you got 'scapegoated' a bit. However, White Mage is always the scape goat. People make mistakes/pull more mobs than they can handle and when you can't save them=your fault. (In part because good whm's save people from a lot of their 'idiot' moves). So throw your gamer Stoneskin up and be prepared that when things go south, Tanks and WHM's typically bear the brunt of the blame...whether fair or not. Just do your best, and improve each time. Which is sounds like you are doing. Fails happen.