I use medkits mid combat a lot, but then I also play solo a lot. Wait, doesn't the game keep going in anything but the pause menu, even in single player? I don't know, eventually I got to where I don't really use medkits anymore. I'm playing the Siren and I have the ability that makes me regen health while in phasewalk, as well as the skill to lower the phasewalk cooldown. so phasewalk is up a LOT, and it regens probably 1/3 to 1/2 of my health every time I use it. Add onto that the fact that I've been sticking exclusively to shields with "very fast recharge", so that when I take a few shots, I just have to duck behind cover for a second or two to get my shields back.
Though, I've noticed I'm playing Lilith more like a standard FPS. I use phasewalk for HP more than anything else, and I steer clear of elemental weapons except for my sniper rifle (and I prefer explosions because the damage is instant. Corrosive and setting them on fire take too long to kill). The lack of damage found on weapons with elemental procs seems just too severe to me. Why have an SMG with 40 dmg per shot and x2 corrosive when I can have one with 80+ dmg per shot? (same accuracy and fire rate.) You know the 3 part (3 rounds) quest line of surviving in the arena that you get early on? In my first playthrough I needed to be like 3-4 levels above the recommended level to complete that. On playthrough 2 I did it at the suggested level and it was beyond easy, even with non-elemental "badmutha" skags, which should have been more resistant to my SMG that had no elemental effects on it.