If you ever feel the MEA are overpowered, sit your Brits or USMC in cover, and sit your big scary good tank in cover, and see what happens then. MEA have a lot of firepower, but you have to recognise, as I did when playing with and against them, that MEA will break their opponent by killing his infantry and not his tanks. Even the Type 99 cannot be taken down by MEA type 29 RPGs in a single shot, and it is the use of the RPG for clearing infantry from cover that makes it an invaluable weapon. MEA players need to recognise the utility and vulnerabiity of all enemy infantry to RPG fire. RPG fire is unlikely to destroy a modern MBT (it literally can't outright kill a Challenger and only Kornets on the fragile Fedayeen can do so to an Abrams). On average 72 RPG-29 shots are required to destroy an Abrams. Only by getting behind and above your opponent can you lower these odds. Firing these shots at enemy infantry will probably win you the game.
The MEA simply have to kill infantry to win. The Zulfiqar is no match for Abrams or Challengers, but is superb for destroying infantry strongpoints.
Fighting MEA a number of tactics present themselves. Almost all of them involve the use of cover and concentration of force. The MEA are a horde army, and while your opponent could mechanise them using technicals it is unlikely he will.
The MEA have very little that can take on your tanks and your infantry are superior and for Brits and USMC have an armour save. If you can set up second refuse a flank. If you set up first then a mechanised force can redeploy to refuse a flank and a non mechnaised force can dig into cover. Ready your MGs. This gives each fire team 7 fire dice and 11 dice suppression. This means you will start to slow down your opponent or choke off retaliatory fire. If you can take one action away from a squad then they must move or shoot in their turn and then rely on a possible reaction to fire for a second action. Tank cannon are invaluable for erasing groups of infantry, particularly combined with the two MGs a tank mounts. Using your infantry to protect flanks you can dig in and wait. The MEA will be throwing RPG fire at you, but unless they are willing to charge in they will be taking tank and MG fire in return and they will come off significantly worse. If you can obliterate one part of the enemy force it gves you a void to exploit with tanks or lighter vehicles (the chinese Norinco, in a group of 2-3 is an excellent infantry killer and makes an effective counter thrust).
If you can refuse a flank you don't need me to tell you what to do, launch a flanking maneuver with tanks/mechanised infantry etc and destroy the closest squad, then the next closest, and roll up the enemy line. A smart opponent will pull his troops back and then use his numbers to nail you, an opponent caught off guard will aloow himself to be destroyed piecemeal, piting militia against professional soldiers with armour support.
It goes without saying to always take a tank if you fight MEA, and particularly if you are Chinese, keep that tank in cover to prevent instant kills.
MEA are not unstoppable. They can be beaten. They can be crushed.