So I tried my first Heroic MT run yesterday with a guild group- generally all in T5 equivalent gear. Our group was:

Feral Druid
Fury Warrior
Fire Mage
Beast Hunter
Holy Priest

Which seems like a pretty well rounded group to me. We blazed through the instance (we wiped once on Vexallus because of bad add management), and then we hit a complete brick wall when we got to Priestess Delrissa.

We had:

Priestess
Demon Hunter + Pet
Arms Warrior
Fury Warrior
Warlock + Imp

After 2 wipes realizing that the warrior's fear was not going to be enough of a CC, we swapped him out for a warlock. With this make up we were able to get very close by banishing the hunter, sheeping the warlock, hibernating the hunter pet and trapping one of the warriors (apparently Seduce does not work on any of these adds, which we found out the hard way). We had no problems downing the Imp and the Priestess quickly, but unreliability of the hunter trap meant that there were two warriors running around interrupting me (the healer) and we wiped about 4 times in a row with not being able to get farther than 3 kills. We had to eventually call it as we had to go to SSC anyway, but (not to sound arrogant) it really baffled me how horribly we did on this fight.

The main problem I had is that I feel like if I went in there every time with a similarly geared Pally Tank, 3 Mages, and me, we'd never have any problems (as the Pally Fear, Sheeps, and Frost Novas are plenty of CC). With the fight set up as it is now I just can't imagine how, at my gear level, I could ever even consider bringing a non-CC class such as:
1) A warrior of any kind
2) A dps shaman

Until I'm more comfortable with the fight I'm probably going to even shy away from Rogues, non-surival hunters, and druids.

I'm going to try the instance again tonight with the "ideal" group that i laid out above, but does anyone have any tips for allowing me some more flexibility in my group building? Am I just a noob and missing some easy fix here?

It's an arena match in the middle of an instance versus a team with a lot of hp but poor coordination/tactics.

Good tactics for Delrissa:
-Bursting someone down on the pull if you can
-Burning/stinging/draining the healers' mana (Delrissa does nothing after she's oom).
-CC/kiting/silencing

It's important to know that aggro doesn't seem to work traditionally... Have your tank swap to dps gear and get to hamstringing/dpsing/stunning or, as a Paladin, helping out the healer

I'm an Ele Shaman, and while CC classes are useful I felt I was useful as well. Tremor totem, grounding totem, purge, bloodlust, frost shock and Earth shock are very good assets--not to mention decent burst.

Uh, yesterday we did it with a less than ideal group with no problems (only wiped once on Princess because of feared into a pack we didn't clear). Our comp was: Enh shaman (myself), warlock, rogue, feral druid, and alt resto shaman. Granted, the rogue and warlock are basically geared out in full t6 and I'm almost up there, but our CC was very low. For Princess, we: sapped a warrior, feared the rogue, blinded the warlock, and torched Princess. After that, we worked the adds down one by one. Granted, bringing 3 mages like you said would easymode the instance, but it would trivialize every other instance as well, this is no different. Probably at t5-level, you can't burn down the princess as quickly, but if you coordinate interrupts, I can't imagine how you couldn't kill her in 10-15 seconds at most. She's extremely soft and only needs one interrupt and a dispeller to keep her from healing too much.

I would have everyone wearing HP gear as they should all expect to be attacked since as the previous poster pointed out, aggro isn't very traditional here and keeping aggro on the boss is less of a priority. Churn and burn works better.

The real pain in the ass in that encounter is the naga warrior. I've only got around 5k-ish armor in my leather/mail gear and his MS was hitting for 3.5-3.8k, and he was getting crits here and there over 4k. If you take a group that cannot CC him the difficulty ramps up tremendously.

My first run of the heroic mode we did Enhance Shaman, Feral Druid, Hunter, Prot Warrior and a Holy Paladin. Basically little to no CC, all of us T6 geared, and we got creamed over and over.

Delrissa is not hard if you can manage to get out of the usual pve mindset and treat it like an arena fight. Wear PvP gear if you can. If you can't CC the melee you can snare and kite them. I did it as a prot warrior and was wearing dps gear, I helped burn down the priest and then intercepted/hamstringed the warrior and rogue. I think most decently balanced groups can do it if they make full use of their abilities.

I'm also a holy priest as well and my approach to this encounter was to basically treat it like the last 2 bosses in heroic Shattered Halls and wear some hp gear. [Spyglass of the Hidden Fleet], [Commendation of Kael'thas] in trinket slots (ironically the latter drops off this boss) and some gladiator pieces were fine, being in the region of 10k health meant I could take 2 hits from the warrior guys without dying. Can't hurt to use the 20 stamina food since it's so cheap. If you have a composition that keeps cc'ing you then you can also wear the PVP trinket.

Try and keep yourself shielded and PoM'd as much as possible since as Zifna mentioned the mobs don't maintain a normal threat list and you will "tank" them quite often. Health potions, instant heals and Binding Heal are all really nice here as well as Fade and even Psychic Scream if you pull them back. Wear the S3 gloves for the equip bonus.

We found it useful to cc whatever we could although did try it with only a warlock for cc last night, and always nuked the Priestess first. Dispel her Renews and interrupt her heals, she has very little hp and makes it somewhat easier to kill the rest of the adds when she is gone.

The Princess fight is definately one of my favorite encounters in the game just because it treats it like a PVP fight in terms of the mobs abilities and random aggro.

We went with...
- Prot Paladin
- Warlock
- resto druid
- mage
- combat mace rogue (me)

I sap the shadow priest, warlock banishes the demon hunter, mage takes care of sheeping the rogue. Our prot pally will jump on the warrior while I basically solo the Priestess. In this fight im running wound/mind numbing and the priest drops very easily after I start popping cooldowns. Basically the more cc you have the more trivial it becomes.

Hm, I can't say for certain that it does. I got the impression that the mob moved away from me but it could have been that it was going to change targets anyway, or someone used an ability to grab it when they saw it was attacking me.

Speaking of the Heroic, how are people killing the 2nd boss and dealing with his adds on heroic mode?

We had a lot of trouble with the small orbs he puts out, not knowing whether to kill them in groups or even who to kill them with, ranged or melee. Granted, I could cloak a lot of the dmg, but that's only 5secs which even with a t6 group, is not a lot of time.

The orbs do 2000 damage a second or so and have barely any hp, not killing them is all sorts of stupid.

Our first group (entry-level T6 gear) was:

Prot Paladin
Arcane Mage
BM Hunter
Shadow Priest
Resto Shaman (myself)

We ran into:

Priest
Rogue
Shaman
MS Warrior
Hunter

First pull was brutal; the tank got kidney shot on the pull, I got gouged and focused down in a matter of seconds. We ended up sheeping the shaman, fearing/trapping the MS warrior, and burning down the Priest while interrupting/viper stinging.

Having the tank in DPS or Healing gear definitely helps as mentioned earlier in the thread. That rogue is certainly annoying though.

As for the 2nd boss, we have the mage kill the first 3 or 4 adds, ice block to remove the debuff, then split out the remainder of the odds between the group (A single earth shock was enough to take them down for me).