Just for anybody else finding this later, I'm always trying to sell people on KA bards.
Bard & Bst's big addition to melee group is weapon delay reduction (haste v4 aka 100 hands effect.) Bard's Quick Time (-14.5% delay) is 4 min buff/10 min recast so it covers all Named or has 40% uptime. Beast's Dicho/Dis Fury (-33.8% delay) is 20 second buff/1 min recast so it's up about 33% of all fights.
Bard provides a stacking +25% overhaste via aura/song (haste v3). You can get a weaker permanent version of haste v3, 8% to 16%, via those
item clicky AA though.
Bard depends on song selection but can provide +190 atk, +45% spell dmg, +40% triple atk, +22% flurry and +35% pet flurry. Plus a variety of melee procs (up to 9k) or AC buffs for the tank (up to +400AC actual armor gains.)
BST adds to group about +1200 atk with Tala'Tak, Shared Ferocity & their Focus.
Each has a melee group Focus AA too: Bard (+45K to next melee hit or DD) or BST (+7.2k to next 20 melee atks)
Great group burst/burn buffs too. Quick Time (haste v4, +1400 atk, +90% accuracy), Dicho/Dis Psalm (+1.8k-18k melee dmg scaled versus weap delay & +7.5K to fire/cold/magic nukes) & Group Bestial Alignment (+50% base/skill dmg)
BST & Bard also provide the best stacking endurance regen/boosts. Using Breather on your melee toons is often enough, but if you want more these two can add a lot.
BST's pet can backup tank for battle rez and Bst can be setup as a backup healer if needed.
Sham: Between PactWolf/Focus/Tala'Tak they provide roughly 15K hp, 600 atk and +11% to all skill dmg. Their Roar group buff line adds a 14K dd proc to melee hits.
Weaker on AC buffs than cleric, but provides 11% evasion bonus which I don't think you can get from any other class. I paired my Sham with a Pally tank to get watered down cleric buffs for the group, but you could also swap in a cleric merc to redo Assurance as needed.
Sham's epic is still useful DPS boost and their burn AA Ancestral Aid is a stat buff that raises group atk by another 240 + HoT.
Have a great selection of heals, their BP clicky is an emergency group heal and sham can keep 2+ HoTs on the group most of the time (Cloud/Roar) which reduces need to swap to heal non-tank group members.
Cleric: In addition to better straight heals and more insta-heals from epic 2/DivArb/AA/clickyBP, Cleric brings HP aura (+14%) and straight melee mitigation via aura (4% mit) or Shining (10% mit plus heal procs). You may have to read up on your tank's mitigation abilities/disc to check stacking, like it doesn't stack with Wurmslayer mit.