I think a rechargeable roll or dash ability would be huge for the boss battles and fights against some of the bigger enemies in this game. There's been plenty of time where I just can't dodge the attack in time due to slow character movement speed and bad luck with the upgrade machine. What does everybody else think??

In my experience slow, small movements give you enough distance to dodge most attacks, including against bosses; even if you have to stop shooting for a moment. The rare times where I would use a dodge roll/dash are usually solved by hero abilities, especially ultimates with their invincibility. If slow kiting, well-used abilities, and brief pauses in gunfire aren't enough to avoid taking damage then you probably haven't built enough turrets.

Noted the suggestion, but I think the dash will require a "bit of work" as potentially involves VFX and other members, so I won't make any promises.
As @C0deR0gue mentioned in most of cases, small movements + shoots make the work!