See people that say "DOT build does more dmg because they dot more people but have less impact" bothers me. If you know ANYTHING about Assault at all, you realize that 2 of their major damaging abilities leave dots. But that does not mean Assault has NO burst.
I used to play Gunnery and I would get frustrated when I started firing Grav Rounds. Every enemy with half a brain sees a big blue beam and goes "EASY TARGET" then jumps you and focuses you down. Its easy to notice and hard to escape people.
As Assault you are not only mobile, but also able to kite people alot better with HS. Your damage feels less bursty, but I can promise you. When I want to burn their healer down, I can focus and burn. I use up ammo quicker, but I can burst more than a Grav round spec.
In the end I feel it goes like this.
Gunnery: High Sustained Dmg. Low Mobility. Great Turret for helping team.
Assault: High Burst or Low Sustained Dmg. Medium Mobilty. You arent just a single role. You can burst or sustain. And depending on Ammo usage depends on how much burst you do.
I feel that Assault has more ways to be played. It has great situational combos. You can DOT every enemy player and prevent a cap, while keeping pressure on the other team. Or you can burst down their healer when your team needs it. You have more options than just throwing out steady high damage.