You do know that the guardian, is a slow, highdamage, class, that can kill a lot, but not catch them....
With a sword you can teleport forward every 10 - 15 seconds and Judge's Intervention gives you another. There are a number of ways to gain Swiftness, and you can have a skill to bind an enemy to you. I'm sure other classes will be more mobile, but a Guardian should be able to get to a pretty high level of mobility.
A guardian can be equipped and traited to be very mobile. There is one trait that makes your standard sword attack give you swiftness on a crit, and another(stacking) trait which makes that same standard sword swing crit chance 50% higher. On the same weapon you have a teleport, and one of your last 5 universal abilities is a teleport all on it's own.
That's just off the top of my head, ontop of strategic barriers I'm sure there are other ways to close a gap(and I know of at least one way to make one, if need be).