All time when you have a party with a hireling, I note this:

1.- Every hireling take a party spot.
2.- Hirelings don't have enough intelligence.
3.- The most important hirelings are the clerics, and if you want they heal better, you must put him on aggresive behavior.

PROPOSAL:
-Turn hirelings into a second pet-

ADVANTAGES:
1.- No more spots filled.
2.- Intelligence will not be a problem anymore.

DISADVANTAGES:
1.- More lag, more work for servers.

COUNTERMEASURES:
1.- Let the game client, calculate the behavior of the hirelings. Server will be free of those calculations.
2.- Limit hirelings to only 1 per player. Again less calculations.