I have done all the HNMs and Faction NMs since the release of Jobs, and our experience so far is:
Dodore: Can be done w/ 4, but is messy an annoying. Basically, pld takes Dodore, and 3 blms zerg the links. Very dangerous strat, since only the pld has raise, but it can be done. Best pt setup we have done is 1 whm, war or pld tank for dodore (personal preference is for pld), war for links, and an archer, everything else is just for killing links.
If you are going for drops, skip the blms, they kill too fast, and mess with chances. Use War to break tail (maim), and war/pld to incap eye (Skull Sunder, and new pld ability, I forgot the name off hand).
Great Buffalo: Still would recommend a party of 6 for this annoying beast. Arc and blm best, 2 healers, preferably whm, a pld tank for dmg reduction, and it is only a single target. DDs on a hill, mages off to a side, and tank with their back against a wall. Pld should use Aegis boon to block the charge ability. A skilled pt w/ drg can trip him, giving you good down time, and tank should work on incap.
Goblin: Pld main tank, war off tank links, a single whm can handle cures, but a whm per split and either go the blm zerg route, or melee, with stun. Melee groups should focus on a single mob at a time to prevent being overrun by bombs and hail marys. Incap is a pain on this one, as it is easier to kill the boss then it is to actually incap him. Multiple plds works well, other than that, I don't remember other abilities that can hit arms.
The Peiste is cake. This can be done with 3 people, a whm, dd, and war. The biggest issue here is keeping the whm from getting hate. The trick here is not doing weaponskills while his eyes are glowing, and everyone should have drops for petrify (spine drops? I can never remember which ones). Only the tank should be infront of the mob, and the dds should stand to the opposite side of the healer forming a triangle around the mob. This will prevent the entire party from being petrified, and if mob switches aggro when the tank is petrified, whoever doesn't have hate should unpetrify the tank (either esuna or drops) as fast as possible. And remember, as long as his eyes are glowing he will continue to petrify anyone infront of him.
As for the leves, they still require 4-5 people. With 4 people, the mob count is still very high, and their damage output is still very painful. You want to pull one group at a time, kill the weakest mob first, and work your way up. Leaving the Leve NM for last.
For the Drake, that can be hard. Consistantly, they are too grouped together, and drakes aggro to sound and sight, so walking and staying behind them is necessary if you need to go in for a close pull. The drakes without bands are the weakest (don't remember if they show up in the NM run or if it's only the one before), then the Amalja?, then the drakes with bands, then the NM amalja, then the NM drake.
for the buffalo, it's a weaker version of the great buffalo, SS and regen can keep melee up, and when the other mobs show up, a second tank keeping them busy should get the buffalo down (it's been a bit since I beat him, don't remember much of the specifics). All and all, he was the easiest of the Factions leves.
The wolf was a Pain. Hardest part here is that the wolves always move around, making weaponskills a pain, and for Drg, any linear AoE can wake slept mobs. Which, the best bet on this one is to sleep what you are not killing, and focus on the weakest mobs first, and move up the chain. The groupings are very easy to only fight one group at a time, it's easier than the drake, but a bit harder than the Buffalo. Definitely can be done with 3 people, just time consuming (we ended with 5 minutes left on the clock with a war, drg, and whm).
Anyways, that was my experience with them. They are still fun, but yeah, none of them require a full pt. a balanced pt of 6 is no problem if you are doing a pickup pt. And other than the buffalo, pretty much any party makeup with any tank and a healer works fine.
The buffalo is a pain, and he does have a hate reset move which makes him more annoying. But he really is only hard if you are going for the drops.
Oh, and I almost forgot the Ram. A party of 4, war tank, a whm, and dds focusing on one mob at a time, tanking out the non-NM ram first (to cut back on knockback dmg) is a cake.
For the most part we found that other than Dodore and the great buffalo, AoE did more pt distruction than it was worth, and single targeting mobs got the fight over with faster and smoother.
(Please note, this was from memory, and may have some inconsistencies, but the overall information is accurate).