Well from what I know and my own experience the bosses in Avalon are pretty tough. But then again that all depends On yourself and how well you do in battles. For myself though, Im no pvp warlord or anything close to that and I find them really difficult. So its definitely suggested that you defeat bosses along side other wizards. But if no ones there to help you I simply would buy a bunch of shield treasure cards and then defeat the boss yourself. It just Takes much longer or maybe even 2 tries but it'll work.The bosses start of with a huge amount of power pips as usual. And there seemed to be a lot of storm and fire bosses, but thats my opinion. Now the enemies are really easy. Although some quite annoying. Farther into Avalon there is enemies that will stun you. And the ice enemies will put the guardian shields up all the time. And this of course makes defeating them longer and more boring. And Im sorry i dont have lots of information to give you though I hope I have given you some sort of helpful info. lvl 80 lvl 25 lvl 53
The Avalon bosses have health ranging from 12k to about 16-17k. They rarely use any spells above rank seven, and mostly have no cheats. Bosses with cheats have incredibly minor cheats, like Black Annie and the now heavily nerfed Young Morganthe. Minions have health ranging from 2k-4K. There aren't many collect quests around them, and they only really use rank 4-7 spells. There are a few collect quests, and I found them to be terrible, but nobody else minds them. Health wisps are a common sight, and bosses are uncommon. The areas are really short, leading to a world that lasts 2 days if you put your mind to it. I literally blazed through the world starting from around the halfway point this morning. Avalon is a joyride more than a slog fest (not for me though. The drop rates for collects didn't do me good D:) so I think you'll like it a lot like everybody else.
As a guy who finished Avalon half an hour ago on my life wizard, I hope I helped the least bit.
Avalon is pretty easy at the beginning. (High Road Cyer Lyon etc.) But when you get to the Wyrd things start to change. um, I'm at Upper Cyer Lyon (end area kinda) and things have been getting hard. But, Cassie the Ponycorn gives you mass prism (72) and another person gives you your spear (80).
.The bosses start of with a huge amount of power pips as usual. And there seemed to be a lot of storm and fire bosses, but thats my opinion. 
just cant get it right.