I've spent the Rift open beta weekend finally doing some testing to see what I'd like to roll up when the retail servers arrive. The exercise has left me simultaneously impressed and concerned about the variety of the soul system.
Right Souls, Wrong Time
I was curious to try then caster clerics, and a post by Ravious at Kill Ten Rats suggested that I pick up Inquisitor, Cabalist, and a misc healing soul.
So there I was, at level 4, with 3 points in Inq and 2 points in Cab. My spell list consisted of a nuke, an AOE nuke, two dots, and a channeled spell that is nigh useless solo because you lose volleys whenever you get hit. I could manage one mob, but aggroing a second mob pretty much meant my immediate demise.
Then I hit level 5 (gaining a point), picked up the Sentinel soul, and went to the trainer to respec. When the dust settled, I had four points in Sentinel and 2 points in Inq. The character lost the channeled spell, but picked up another nuke with a 30% snare, an instant heal, an instant damage attack, and an endurance buff. Suddenly, a single mob was easy, and even a second mob started to become manageable by applying dots and healing. It was like getting an entirely new character in a single level up.
Know your roles?
The soul system does look like it's going to be a lot of fun to play with; no matter how badly you bungle your character initially, there's probably going to be some combination that's actually usable. Every single level potentially opens a previously impossible combination of abilities, especially as players get a larger pool of souls to choose from.
That said, first impressions in this system can be challenging, and the learning curve is a potential issue. Based on my first attempt ("I'd like to be a caster priest, so I should take both caster priest souls"), I would have concluded that caster priests just aren't very good. If I'd started with the other build, I might have reached the conclusion that the game is "too easy". Throw in some of the inevitable balance issues (I think my Riftblade warrior did better ranged DPS than a mage I tried) and it could be a long time before things settle down in Telara.
P.S. One of the more intriguing concepts is the Void Knight - a warrior tanking soul that specializes in destroying anything with a mana bar at the expense of not being able to use most of its abilities if there are no casters around to smite. This just wouldn't be a viable class in a normal game, but Rift opens up its dual spec option early enough to have highly specialized souls. Again, time will tell whether having this degree of specialization causes problems for PVE (and/or PVP) balance.