The most common place is the new wilderness rifts. If I'm not mistaken, the closest one to a bank is in level 9ish wilderness north of edgeville. They have monsters ranging from moss giants, to fire giants, to zamorak warriors, to giant rock crabs, to nechraels, etc. Summoning helps there (if your strong enough to fight the monsters in the first place).
Dagannoths are multicombat too... as well as many guard spawns for lower levels. I can't really remember any more off the top of my head, but I'm sure the runescape website has something about it in the knowledge base
