What changes would you like to see in 4th job skills?

They also discourage partying because it's tough to find a party member that will not actually slow your exp rate down

 Off topic tangent about the party/XP system. Ignore if you don't care.

This is a common misconception. Due to the way the XP gain formula works if throw HS into things a mage partying others gains more XP than solo by at least 10% as long as they're 19 levels above the other leechable party member ( examples - 143 AM and a 122 bishop can party just fine. A 170 mage and a 145 bowman can as well if a leechless HS mule is in party to provide HS).

It's somewhat limited since you cant have a full party of 6, but realistically an ultimate spamming mage doesn't really leave enough targets for more than one other 4th jobber most of the time.

Still, 110% plus thier kills means mages do have incentive to party they just don't know it half the time. This is one of the reasons I argue HS mules do more to aid partying in general, than to undermine it, because it frees people to party with any class, not just clerics and bishops.