Useless idea IMO. The reason people die to bosses is because they're not familiar with their attacks. Fighting huge swarms of mobs and fighting a boss are two different things requiring different tactics and perhaps even a different class. People will also find things that work for them, there is no "one" solution.
I personally find that against huge numbers of swarms, running away, then using the air version of Magnus on a Cleric takes care of that problem nicely. I found the Cleric to be good for Surt as well since he doesn't move an inch.
Stuck on Hrungnir right now, but I suspect the Mage is my answer for that little problem.
I played the game all multiplayer when the game first came out, and boy did I struggle hard when my party couldn't handle a boss. But farming bosses offline has made me a better player I think, I die way less often anyway