This was one of my concerns as well. However, when you pick your calling (Warrior, Mage, Cleric, or Rogue) you have basically assigned yourself ability options. I'll use my experience in beta as an example. I created a Marksman (Rogue calling). After a little bit, I got the option of another soul to pick up. I chose sabateur. (Traps interested me, especially with how squishy I was with multiple adds). There was no big crossover here, especially as I wanted Sabateur for utility, not for the deep abilities. So I progressed. And I came to realize I was starting to get beat up on a lot. Not dying, but always taking damage. So at the next option to pick up another soul, I went with ranger for the pet. This turned out to be quite the blessing. And then I noticed the rangers abilities looked an awful lot like the Marksman. My immediate reaction was "Oh no, this is going to be terrible." I could already see my hotbars getting flooded with abilities. But it actually worked out quite well, as you can simply remove a lot of abilities from your hotbars. Marksman had a generic combo point building ability that did practically the same as the Rangers generic combo point builder. The same can be said with the finishers. Look at your options, and choose the one you like the best. Its actually more simple than it first appears, that I can promise you.
I can also say, out of 50 levels, beta3 took you to level 20. haha Who knows what the future holds!