The first step to success is letting go of the idea that you can stand in one place and absorb damage. You will have to move, you will have to juggle aggro with the other heavily reinforced characters, and your League as a whole needs to be continuously taking down enemies to make sure you're not overwhelmed.
Character index
As Silver Gale stated, these new Trials are not about using tried and true methods of combat - certainly in both Trials you simply can't stand in one place and pound on the enemy (Nightstar & Marauder.) Instead it's about sharing the aggro, moving around, keeping in mind what needs to be done.
12 people pounding on Siege while hordes of 9CU's get stronger? May, for a moment or two, shift your attention to clearing some of those jerk faces.
I ran a BAF last night that almost won (the first time we dropped Nightstar and Siege, we needed to be about 1 second faster with piling on the damage. We failed with them both down to about 2% health), and what we did on our 13 man group (something around that) was split into two teams. Team 1 focused on the AVs, while team 2 focused entirely on taking down the reinforcements as fast as possible. We'd pulled the pair over to the tennis court, so team 1 could jump back and forth between AVs, and team 2 was near one of the main reinforcement points nearby, so could jump them as they appeared.
The main thing is that, yeah, you need to seriously reevaluate your toughness in these things and your ability to take on groups alone. Multiple bosses represent a real threat to players, and even LT's can be dangerous. Stick together, play as a team, and make sure there are some people set to jumping the reinforcements fast, including damage dealers and supporters.
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Yeah, the new trials can't be done like a typical TF. Not easily, at least. It's more like going up against Hamidon: Everyone needs to know what they're doing, when, and it needs to be executed quickly and carefully. Everyone needs to be kept in the loop.
Of course, it can be done with an entirely random team. The clincher is just that everyone needs to know what to do. Which is why I'm never going to run one, because good god, I'd have a heart attack.
It's not that hard to run once you've become familiar it with you know the phases and how they work.
That's what I keep hearing, and why I am trying to set up a "playdate" of sorts with some of you skilled players who have it down, to show me what I'm doing wrong. 
I am willing to learn, I just need to figure it out I think.
I hope to see you there on Monday.
Elvnsword
(@Enforcement, aka Liberties)
"when i can savagely beat sheep while issuing ultimatums and torturing people, then i may go back into it" -vara nocturne
Not enough Evil...
I take it back NC SOFT is enough evil for anyone...
Add my main to your friends list, "Voodoo Girl."
If you see me online on that toon, most likely I'll be leading one of these iTrials.
You can still treat the trials like any normal TF as long as you have the resilience and damage to compensate.
I think the primary issue is the queue system, where I'd say about 7 out of 10 PUGs in new content tend to fail. People queue up and then decline or leave, which cripples your chances. But like Voodoo said, knowing what happens ahead of time and how to move with the flow rather than being left behind also strengthens your chances. We just followed Marauder around wailing on him but that was because there weren't any reinforcements to worry about by then, we knew the primary concern were his portal and we had that covered from the get go.
Hey everyone,
I havn't had a lot of luck with the new Incarnate trials. I don't have a lot of regular teaming partners, but my Brute, Liberties, is feeling like tissue paper out there.
I was hoping someone could take me under they're wing here, and show me what I am doing wrong, or what I need to do to make it work out better, so I can get the BAF and Lambda Trials completed. I am willing to try it again, but am at 0/15 now, and it is a bit disheartening for a brute who has previously tanked Recluse in the Statesman's Task Force, Riechsman, and an Enraged Bobcat...
Please send me a PM here on the boards if you would be willing to have me along next Monday (next time I have a chance to sit down and play for a long period of time), and I will come by when you specify and try and lend whatever help you specify.
Thanks
Elvnsword
"when i can savagely beat sheep while issuing ultimatums and torturing people, then i may go back into it" -vara nocturne
Not enough Evil...
I take it back NC SOFT is enough evil for anyone...