I don't really agree with the first 2 points since theres always the heat orb cannon which can pull you into 2 range regardless of using high knockback shotguns and legs. However the rest, i totally agree with

My way of countering heat mechs: cooldown once per turn and use weapons that use little heat . This will be harder for that mech to overheat you, most heat mechs focus their stats more on heat and cooling rather than hit points.

i used mass deflector/shockwave to push them back pretty far,maybe make a physical mech with good cooldown and energy regen,with one of those swords,and see what happens.

Its certainly getting rather silly, its pretty much the only mech I see lately. Maybe a 2 range multiuse massive heat flamethrower is a bit much?