I am against bringing back the old master mob lead. I agree with leadable mobs being mainly for RP purposes with minor Pk/Exp/Smobbing advantages.
Old Master mob would do the following:
-Help balance uneven pk vs. numbers :
By help, do you mean create an unfair advantage for the side who can lead an incredible amount of mobs throughout 90% of the PK zones?
And Numbers aren't the end all of Pk. 2 Dsers can beat 4 LSers when using zones, fleeing, regrouping ect. They don't A) have to be master dsers to do this and B) if faced with incredible odds 4+ LS vs 2 DS, then they should get low and go into Keep. Next step is for LS to hit inside if they want to continue pking.
-Keep pk going for longer sessions :
Again, I feel master mobs = Steam rolling. So I fail to see how this prolongs pk. And I agree with Isabel, Pk goes on for as long as people stick around / chase / hit. If 5 LS don't hit 2 inside Keep, then that's their choice. Giving 1 of the two Dsers 1 master mob, won't change that.
-Give solo people assistance with doing things(loners) :
I agree that a master mob is a boon for a solo player. It should never replace another player however. Current master mobs can still help solo players.
-Help people who play in low playerbase times of the mud :
Low playerbase times are equal for all sides so, the solo LSer pking will probably fight the solo DSer? I fail to see how a master mob will change that. And otherwise, see previous answer of what solo players (low playerbase times) can do.
-Help with smob group numbers :
I am happy with the master mob dissuasion enforced with emote dmg. 2 masters running around farming all the smobs for no reason and dumping the eq in barrels, while helpful for the barrel feeders its unhelpful in terms of coalition and multiplaying with others. By removing master mobs in general from Smobbing runs more people spend time with more people. This is good.
-QP sink :
I think trink issuing is enough of a qpt sink. Masters leading and pking and then taking scalps from non masters to cover for their mobs death? Is silly. Non masters should get the scalps first, not the guy who lost a mob and is already bonused.
-Help with city quests or raids :
Raids. If you are raiding solo, you're out of luck as an abser. Other than acting as long term bait to the north. As a comboer or dodger, there are tons of DS friendly locations that can be used to allow you to get kills or live forever.
City Quests. 5 masters and 5 old mobs vs 5 masters and 5 new mobs, is about the same thing. It's still a huge group and while your 1 mob with a dark barbed flail won't be able to take out an entire patty anymore, the 5 completely free new mobs will still do loads of damage and require that you buff or rescue them more often.
TL;DR - I feel the current system is fine and master postures/dmg is amazing in and of itself. A "weak" leadable mob that breaks deff and can be eqed is amazing.