Your dodge area is incredibly restricted compared to a 3D environment. Not all attacks will allow you to get back in range in time. You cant just side step and go around them to continue the flow of attack. The concept flows much much better in 3D than it ever will in 2D as they have it here. Just watch the people playing the demo.
There are ways to fix this if you balance other factors right, but they simply chose to shoe horn LoS gameplay in almost verbatim without consideration for the 2D plane restrictions. It ends up coming off as silly and clunky.
EDIT:
Also when Trevor is whip swinging he looks like this;
Your dodge range might be limited, but the enemy is limited to the exact same two dimensions. Instead of enemies shockwaving and side swiping like they did in LoS to keep you in check, they would just focus more on thrusting and chopping attacks. As long as the enemy AI allows for jumping to be a reliable defense (which it didn't in LoS) that point is moot.
And the length of the whip on a basic direct attack is >= than the dodge roll distance, so horizontal range really doesn't seem like much the problem you're making it out to be, and if you're really pining for that extra half-second of hits if you end up too far, an area attack can be anywhere from 45% - 90% of the screen.
I think this guy really is just bad. Everything about the way he moves Trevor screams it. He walks face first into the bosses, and can't time his jumps very well. He also never blocks, and never does much beyond "mash mash mash unsituational attacks". I really don't think this has anything to do with dodge range or mechanical fluidity.
Then again, we won't really know until the game comes out.