Current Group is:
Warrior
Cleric
Bard
Druid
Here suggestions on how I would do it:
Option #1: Add a shaman. While the bard slow might be able ok for the moment, with a shaman, you'll be able to tackle much tougher content. Also, with some of the HP/AC buff and the proc buffs, you'll increase your effectiveness as well. Toss in the debuff, DoTs, and pet, it will be icing on the cake.
Set up some hotkeys to assist the main tank, malo the mob, and slow the mob. Use audio triggers to your advantage for fizzles and resist messages.
Option #2: Add a mage or necro. These two are great for "fire-n-forget" DPS. Once the pet engages, you'll have constant DPS even if you don't do anything else to the mob. Throw in some hotkeyed DD (mage) or DoT (necro) spells to increase your DPS.
Option #3: Add a wizard. Normally, I'd have this one higher, but since you already have a druid in the group, the transport feature of the wizard loses some appeal. Still, it is great "fire-n-forget".
I would have the wizard sit there for the first portion of the battle so your warrior builds up aggro (you'll have to determine the sweet spot). At a certain point, hit your hotkey and you can chain cast your nukes with one hit of a button. Have the hotkey make your wizard sit down. Once the mob dies, the wizard will have time to enter OOC regen while you are pulling and engaging the mob.
Option #4: Add a beastlord. You might lose some of the melee effectiveness trying to box a second melee, but the slow and pet might make up for it.