That's okay for contracts as they are heavily scripted. But I usually play vs EXTREME, with litteraly tons of tanks and units. I first having my heavy tank K60A2 on front, and a nice space between my other tank with 120mm guns and rockets.
First thing I do, is create space by two taping a few buildings with my HE heavy rockets. Once I have a "kill zone", I place my KOM 319 PD not far behind my heavy tank so it'll kill all rockets and atgm coming in.
Then I put in the back my B30A1P with full optics, passive sensors, passive emission and all (it's basically cheating I can see where all the ennemies come with a VERY good accuracy and distances). Plus I got a field of view AND a distance coverage that will be at least 2X times the best recon the ennemy have.
But my go to anti tank is my B30D equiped with 2X 2AT2 anti tank missiles. Its missiles reload is totally busted, and I can one tap almost everything from the front.
Combine with all the rockets my other C3A7 tank (plus its 120 gun and all the RR guns and 30mm I mounted on empty slots of the other vehicles), it's armageddon xD.
I get you can be "tactical" and slow for small missions, but once you get on this degree of difficulty I find infantry "meh" imo.
Contract 3 sees a reinforced assault force attack you ~15 seconds after mission starts with little breathing room until you've killed 8-12 vehicles, but my infantry still smashed multiple heavies.
They are very micro-intensive and slow, and are most suitable for methodical players, which is fine. Not everyone has to like infantry.
But they're incredibly strong in the right circumstances, and not at all underpowered.