Well, time for me to give my 2 cents

First off, I just want to say that I absolutly love your paintings- all of them. I don't really have anything to say other than that they're absolutely amazing

As for the models, they follow suit in being beautiful. The only critique i can make for the medic is that i feel like her jaw is a little narrow beside the mouth- the whole head seems to taper to a point rather quickly- not really a problem, more preference, but i thought i'd throw it out there. After all, this is just me voicing my opinion.
For the heavy, I'm having pretty mixed feelings. On one hand, the craftsmanship is beautiful- the model looks great. On the other, I kind of feel like the design is a little plain, and much to soft to be a substantial and equivilent counterpart to the male Heavy. In the top two close-ups, I don't much care for her face shape- I think that the jaw feels a little too round, and that a more angular jawline might make her fit a little bit more into the tf2 theme, and her respective class role. I also feel like she needs a little bit more of a brow- she can afford to have it protrude a little more, and her nose could be a little flatter to compensate. All in all it just feels a little too soft for my tastes.
In the bottom picture though, I like the face quite a bit more- she looks quite a bit more natural and intimidating, as she should be- may just be the angle, but I'd still go on my impressions of the close-ups, since I'm getting a full view there. Also, her body seems a bit disproportionate- her gut doesn't look quite natural, and her hips/butt protrude at an odd angle. I'd suggest that you try and fill out the thighs and hips a little more, as it could potentially make her look a little more "normal".
I am making a lot of criticism here, but believe me, this is all relative to your amazing level of quality and artistry that i'm seeing in your other pictures/works. I'm not at all saying that it's bad, hell, it's thousands of times better than anything i could ever do, but i'm just trying to nitpick and just suggest whatever i can to help- a little constructive criticism is always useful, i'd say

Oh, and one other thing- what did you use to do the models?