I started off with 1 group until T3:
Pal, Shm, Clr, Brd, Rng, Mag
It was then i started to struggle too.  I could clear it, it wasn't difficult but it took too long.  The DPS just wasn't there, so i ended up making a second group:
War, Dru, Enc, Bst, Nec, Wiz.
The idea being a self contained group using Sune for buffs, until i found out the Enc can't pull on this server!
Anyways, the War has come in handy.  He's not up to scratch in gear but if things start going wrong and i panic-press the wrong buttons killing the Pal, the War can and has saved the day a couple of times.  The extra DPS has been nice too as has the Evac buttons 

T4 was a real difficulty even with 2 groups.  The Fennin Event spawns guards at the end i just couldn't survive without some outside help.  The damage they do is ridiculous.
T5 is still a work in progress.  Or, Xeg is i should say, but that's down to strategy and not a problem with Pally Tanking.
Long story short.  If you like your SK, use him.  I've used my Pal up until now with no thoughts of "maybe i need to swap".
I don't know if SKs get the same defensives that Pals do but i would expect they get something similar.  You definitely get the same Defensive Disc ring from ST which you can use.
I recommend 2+ groups if you can.  From my experience around these tiers 1 group is asking for punishment.  The extra tank has saved the day and the extra DPS has saved a lot of time.
I'm even considering making a 3rd group 
