Both your needs share the same solution, which is a proper pathfinding system. Pathfinding is divided into 2 parts, global (get yourself out of a maze) and local (avoid dynamic stuff), and local should be able to make the npcs avoid other npcs in such a way, that when they want to attack the player but there's someone else already fighting with him, they'll avoid him on the left or right. If many people do that, surrounding the player will happen on its own. I suggest that you don't use more dodgy methods like 4 dummy entities around the player, since you'll most probably run into even more problems (what if more than 4 people want to attack the player, or what if the only free dummy entity is on the opposite side of the player than the side where the attacker is?)...
I suggest you take a look at the AUMs which include both Pathfinding (global), and an obstacle avoidance system using c_traces.
there is ai avoiding dynamic objects(other characters) in intense (not sure if in intensex or intense pathfinding).
avoiding dynamic objects is included in Intense Pathfinding 2 and Intense X Copper 0.9. Since you're making a fighting game (sorta like Prince of Persia minus the acrobatics I assume), I want to ask you something..
I was interested in making a short video tutorial on making a fighting game with Intense X, but my models only have 1 unarmed animation. If you want to send me your animated models(which i will only use for the purposes of making the video, and delete afterwards), then I'll shoot a video explaining how to build a game like that in less than 10 minutes using IX, which you may find interesting.
Cheers,
Aris
