I agree; the difficulty level ramps WAY up once you hit the desert. Suddenly, the consensus among most players is that you are required to group to complete the trials. I was really enjoying the lack of forced grouping in GW up to this act. Everything about Ascension is a big fat reminder of why I hate grouping up with random people in online games.
The quality of teamwork in GW pickup group is hands-down the worst I have ever seen in any MMO. It's not just a little worse; it's in a special extra-festeringly bad class of its own. I've seen everything Lionel mentions above over and over. People routinely bail on a team after a single death. Half the players seem unable to stop and regroup under any circumstances -- it's run forward until dead, the rest of the team be dammned! They've never heard of everyone focusing on a single target either; it's a bunch of people each trying to solo a mob. And if you try to discuss strategy, you're usually met with stony silence (or someone shouting "why are you guys still back there? move up and heal me you #@$!#s").
The good news is, you can REACH each of the 3 trials with just henchmen -- I've reached all 3 after giving up on the pickup group scene. Of course, after you reach the trial area, you have to BEAT the trial. The crowds in the mission entry area are much smaller, so it's even harder to find a group there-- as Lionel says, if you're not a monk, settle in for a long wait. I have beaten one of the trials with just henchmen; no luck yet on on the other two.
Grouping with good people >> grouping with henchmen >>>> grouping with random B.net kiddies. I'll be glad to help people do these trials once more folks get up to this level. I'm on as Tarsus the Dreamer, Tarsus the Wanderer, or Tarsus the Tranquil.