The impression I get from Slash Dash is that it's primarily meant to be used as a mobility tool and maybe panic invulnerability. It's damage isn't particularly high, but it excels at getting you from enemy to enemy in the blink of an eye, as well as traversing wide open spaces. One thing I'd like them to do with Slash Dash is make it so its chaining between enemies is affected by casting speed, since it would just make sense.
If anything in Excal's kit needs a damage buff it's Radial Javelin and Exalted Blade. Imo Javelin should scale in some way - it's so pitifully weak its only use without Furious Javelin is nuking low level mobs. Exalted Blade, on the other hand, could do with getting brought in line with the melee weapons of today. As it stands, you'd be better off subsuming it and just using a normal, unexalted weapon, instead. Similar to Javelin, it's being kept on life support by its Augment, rather than standing on its own feet.