Tactician or Commander. Either name works.
Play on the themes of a leader of an army, eschewing physical glory to better command their soldiers into victory. Instead of being a traditional dps, tank, or even healer, the Tactician focuses on giving his allies all sorts of buffs and whatnot. He does respectable damage, but he also increases the damage of his comrades. He has some healing, albeit a very small amount.
Leading by example, the tactician still dives into battle headlong, but it is his commanding cries and banners of victory that inspire soldiers to succeed. The tactician may take a shield to better weather blows, or to take a great sword to dash his foes to pieces. This new spec is not very good by themselves, and requires a group to operate at their very best.
The talents for this spec are interestingly focused on providing buffs to the Tactician’s solo abilities, smaller group based abilities, and for large group abilities. From being able to cast certain core buffs on a larger group of characters to a long CD of summoning a small army of temporary NPCs bearing banners that you can place, the talents are fun and varied. Fittingly, the Tactician will lead the charge in providing a new role in WoW that isn’t DPS, Healer, and Tank. A ‘support’, if anything.
Following suit, other classes could see getting supports. A mage that bends the flow of time to provide haste and mobility for their team, a bard who can shred the faces of their foes while providing unique combat buffs, and even potentially a warlock who makes you “Drink.” Gul’dan energy increases
And for another spec I’d enjoy, I’d enjoy a gunslinger rogue. Keeping the tricks of the trade, the Gunslinger still fights dirty. They throw blinding powder, they kick, they punch, but they also shoot. Keeping it short ranged because a long distance rogue still seems extremely overpowered, the Gunslinger still focuses on ambush tactics and disruption. What sets them apart from Outlaws, though, is that the Gunslinger has reduced mobility. The Gunslinger trades mobility for range. Built around trick shots and building up fancy techniques, the Gunslinger throws grenades, fires their pistols, and waits for their targets to line up just right.
Different from Marksmen, as well, the Gunslingers don’t focus on single massive shots. They also can’t just sit still. Ducking between melee and range, the Gunslinger wants to keep you on your toes as much as they want to keep on their own.