Since people tend to forget about them, I say the Council of 3 Hammers.
All 3 have had nect to no real screentime since ever really. Moria shows up in the dark iron unlock quest, Falstad you do like one quest for in BFA and all Muradin has done since Wrath is show up in the Arathi warfront every few weeks.
Almost every other npc in this thread has had more screentime than all 3 members of the council put together. And the dwarves are arguably THE backbone of the alliance.
Also, besides Rohkhan they are like the only core racial leader to not have their own unique models