Plz tell me you're using the 85mm D5T and you are not stock...
Gun: It has good reload, I could pull 4.4 sec reload with 100% crew, vents and rammer (no BIA though, so you could deffinately pull reload less than 4 sec). The accuracy is more than enough (.37) for a medium if you are going to be flanking, it can snipe in a pinch but isn't its main role. All in all, with mods and crew skills you're looking at around 2000-2400+ DPM, some of the highest for its tier (I think the comet beats it by a fair amount.)
Mobility: This is from personal experience... I actually liked the mobility for it, sure its not the best but it gets you to where you need/want to go. Dont expect to race with it, but it does fine for relocating to that crumbling flank, or to close the gap between the TD that just fired
Armor: Not much to be said here except don't go head to head with other tanks, even tiers below you as they will pen you most of the time. Angling can help you get some lucky bounces, assuming you know your enemy and the gun he has, when he shot, etc. Face hugging can save you some times but rarely is there an opportunity for it; to give you an example, I out DPMed a KV-13 by face hugging him and shooting his cupola. Module damage is not as frequent as you'd expect, an engine here or there but it happens to the russian med line frequently; your crew, though, is another story. The driver will buy the farm almost every other game, and so will your gunner or loader as your turret does little to protect your crew.
Conclusion: All in all a solid medium (in my opinion), good DPM for its tier, mobility gets the job done and don't rely on your armor. Play it as a flanker and support your heavies, hit and run tactics also work. Distracted enemies are your primary targets, hit them 2-3 times and back out... Rinse and repeat. Always remember the play style you like the most, if you're going to be that flanker or if you're going to be that front line guy use your tank to its best abilities. Only recently am I discovering that I wanted to play agressively like Garbad only to realize I do poorly and that I'm a Kewei type of do-damage-and-let-the-pubbies-take-it type of style.
Some rules to go by for this tank:
Rule #1: DO NOT brawl other mediums
Rule #2: DO NOT circle other heavies unless you know you can. I.E.: If you're on a hill fighting another heavy, or you know the enemy heavy has good turret traverse. Done it before to a tiger, just track and circle.
Rule #3: A lot of people underestimate the T-43, use that to your advantage
Hope this little guide/review helps, I might not be the best player or the best T-43 driver but I did pretty good, if I do say so myself. Wish I had some replays because some of my best and also my funnest games were in that little tank, If only WG had created a backwards compatible replay program...
Anyways, happy hunting o7