Medium tanks have more range (40) than handheld AT (35). They are faster and have quicker aim time. It's pretty easy to kite AT infantry with medium tanks and kill models while taking next to no damage.
Handheld AT blobs are quite easily punished by players who know what they are doing. There are plenty of counters: kiting, mines, rocket artillery, HMGs, AI infantry, etc. Blobbing AT infantry is generally absent from higher ranked games. I can understand lower ranked players might struggle, but ultimately it is a strategy game where there are counters available (both on a micro-level and on a rock paper scissors level), and if players can't or won't use those then there is a certain point beyond which balance itself can't help anymore.
Im mainly playing with friends from 2vs2 to 4vs4, we are going up and down in rank usually somewhere between 200 and 600, the best rank I ever achieved was about 120. There it is a problem. So it seems at 2vs2 and up lower rank starts below Top200 already. Thats a hell lot of players. I know it is much less of a problem in 1vs1.
In theory there is always a counter, although the most important next to MG (rocket artillery) isn't available non-doc for all factions.
My main argument in my last post was that med tanks get useless in lategame because they just can't get into frontal fights with heavies and TDs while flanking/diving in gets denied by AT-blob, which does needs way less micro than defending with mines and PAKs. You don't need 5 or 6 squads for that. Given the potency of AT handheld atm, you just need two squads with triple super zook or double shrek and you will force off or destroy every medium that tries to close in.
Even if you used recon before the attack the blob surely comes just in time back out of the base when you start to flank. When you are driving forward you can't stop your tank fast enough to not get hit with an At handheld aiming time of 0.63 seconds.
So it mainly comes down to TDs and heavies in lategame, it could be so much more. Strong handheld AT restricts lategame tank diversity.
Edit: I have seen a lot of complains that it always comes down to TD/heavies. So, there has to be something wrong, when meds have no real place anymore. I'm just saying what is the reason for that imo.