Make the bard slow, maybe just on named. They have a long lasting one and you can swap out an attack/proc buff for it as needed. The big exception will be like ToV Kael or missions where you can't mezz anything, then you want good splitting or AE slows.
I run a slower in every group, but the 25% slow/cripple proc tank belts (Crippling Slicer) help a lot. I don't bother to "debuffall" and slow all mobs anymore, just the main target and let the mezzer get things under control. I feel like slow is still a big deal on Named, but not so much on trash. With trash it really seems like that 2-3 seconds you're casting slow, you should just go damage since the fights are like 10-20 seconds anyways.
That said, you could get higher DPS if you swap to a shammy healer. Shammy is a little tougher to run than cleric, but very workable. The three things I miss from cleric are "shining" mitigation (run EoK wurmy for instead if needed), the big HP boost from cleric dicho/dis heal & DivArb/epic insta heals. Sham work well with war though because they have that direct HP temp buff which knights already get. You'd also get a tiny bit more mitigation on your warrior from focus's stat boost and the 11% evasion buff. If you go shammy, get their epic too. One of the best melee buffs in game still.
Bst is a popular swap in for 6th melee DPS or running Zerk(x3). BST covers a lot of what sham provides + more atk/weapon delay reduc, so if you go sham you can keep cleric for more stacking HP buffs. Zerk(x3) lets you share the direct target debuffs that add to frenzy and use your alliance/covenant (really only useful on named or giants.)
Rog is a totally fine 6th too though. Poisons for all melee and their aura are nice.
If you're staying FTP with no expacs, then grabbing the ToV T1 gear in Bazaar for your tank will put your really high on AC for RoS content. It will feel like you're in raid gear for most areas so slow becomes less critical.