I wouldn't say that there is something like "general minis situations". Every mini is a bit diffrent and it is hard to compare skill between melee character and caster.
1st of all kiting get a lot easier (imo) when average latency (at least for EU players) doubled. I'm saying this both as melee and caster (I play PvP regularly on bs&demo).
2nd, you are not alone in minis. There is a lot of people who don't have a clue or simply don't care, but there are still some good pvpers and often frenzy soldier = dead soldier.
3rd, sometimes you can even meet people who are willing to heal you and help you with their's cc.
It happens that you are left alone (as a caster) with some tank on your back, but unless it is one of those good geared AND skilled soldiers (and there is really only few of them) you can handle this somehow.
And it is not only casters problem, BS can die just as fast these days if focused properly.
I like soldiers the way they are - it is because casters can't just ignore them and as we all know reaching that guy who is nuking you from other side of map is not that easy. How to say it...I just strongly disagree that mages are worse/weaker or underpowered compared to other archtypes.