In your setup, a druid sounds good but these are the things I would consider:
Pros:
Ports....currently you are missing them.
Snare......though this is double edged. If you snare a mob and you wipe, that snare lasts an insane amount of time.......you may be campfiring back to a mob that you got stuck there.
ADPS.....dmg shield, grp wolf, aura
Cons:
The druid's heals are not as fast as a cleric's and you are running a knight. That initial hit can leave you with a wipe especially if you are afk.
KA in default state does not have both in combat rez and out of combat rez. If you configure improperly, you may find youself do a call of the wild over and over on your members resulting in rotted corpses.
You are running a knight that aleady has steadfast/staunch. Druid/Shaman growth line doesn't stack so this will be useless.
Druid will nuke in this group setup but will quickly deplete mana if they are adding any significant dps if they are the main healer.
Druid can add adps with their aura and group wolf but you have a chanter already adding mana recip and IOG. Check stacking issues.
Druid has no ability to recover mana quickly if they die. They have no harvest of any sort. They depend on their wolf form and skin for mana regen. Cleric has QM and VP which at max will recover about 50 percent mana after rez. Yaulp will keep you near max on group content.
I have never been able to get a good stable afk ini for a druid as a main healer (I can use a sham as a main healer, just can't get a druid to work for days on end like I have with the other 2 priests)
Conclusion:
With cleric, you can add 2 caster mercs.
With druid, you will probably still need a cleric merc and add 1 caster merc.