Okidioki, since I am starting to learn all the classes at this time. I can tell you the following:
Each class has it's own movement issues. If you've mastered ranger movement, it does not mean you've mastered tech's or gunner's.
Each class has it's own weapon issues as well.
I think if you have MASTERed the ranger class, you're good at hitscan weapons and hence you'll be pretty good with the tech and need to learn to adapt to the gunner's prediction.
Now, the time involved in MASTERING the ranger class involves aspects of XMP that crosses all of the classes. But I can tell you now, that even though you're a master ranger, and deside to play gunner or tech that you're not on par (or even close) with a master gunner or tech.
In order of ability, this is my semantics:
Master
Excellent
Good
Average
Below Average
Noob
Master Ranger -> Excellent Tech but definitely not a Master Tech.
Master Ranger -> Good Gunner but definitely not an excellent Gunner.
However, I do believe a Master ranger will have easier adaptation and better skills then master tech or gunner switching over to the other classes:
Master Tech -> Below Average Ranger
Master Tech -> Good-Average Gunner
Master Gunner -> Noob Ranger
Master Gunner -> Good-Average Tech
Also, now that I am learning to play Ranger, I can say that switching over to Gunner requires at least one or two full games to switch over to the other class and play it well as I usually do.
I guess the question is, Have I mastered gunner? Some of you will say yes, some no.
Of course there are game specific things that a person that's a rmaster ranger that will be noob at including: turret placement, mine placement. Etc etc.
A Master Ranger can not switch to Gunner and beat a Master Tech, Gunner, Ranger.
A Master Ranger can not switch to a Tech and beat a Master Tech, Gunner, Ranger.
So no, a person who masters Ranger is not a master of all classes, although on initial switch, they will generally be good at it from a battle perspective (but no experience on deployables).