I was thinking more that all a shaman does basically is heal and lay down med-high moderate dps (in a caster group.) It would make more sense to have another wiz or mage providing high dps. If Heals are the issue, then a druid, because they can heal, dps, and they offer some caster bonus debuffs I believe? I didn't list bard first because of desirably, but simply because I thought of it first. I don't know how well bard caster dps stacks with chanter caster dps buffs. Bards do have the ability to pull far better than chanters though. I've been a chanter whore my most of my life, it's only been the past month or so I've been using a bard, and only the past few weeks I've dropped the chanter for a beastlord unless it's mez heavy.
This is my understanding of various utility classes (Please correct me.) If I have played this classes its only been as a box, so most of my info is from that, or reading what I can, and much of it may be dated from 7+ years ago
Shaman: melee dmg bonus, strong group heals, weaker single target heals, cures, moderate dps mostly due to dots., moderate CC ability, ability to rez, HP (ac?) buffs.
Druid: Caster dps bonus (though weakened recently?) strong single heals, weak to no group heals, cures, moderate dps, ability to rez, transportation. I haven't leveled my druid, so I much of my recent info is things I've read, the rest is from before I retired and regularly grouped with a couple of druids. I'm waiting for the next double exp before I PL my druid and ranger, unless I get bored.
Bard: caster and melee dps bonus (though better for melee?) Pulling, CC, mana regen, slows, I've seen llow moderate dps with strong gear but mine puts out low (under 70k) dps. (lots more I simply don't know, the class is a complete mystery to me though I'm slowly learning.)
Enchanter: High caster dps bonus, strong CC, slows, mana regen, low moderate dps.
Beastlord: Melee dps bonus, hp buffs, slows, can tank or pet tank, minor heals, moderate dps.