I actually don't mind the way that meleeing Flesh Pounds works now, and I don't like suggestions that would make it completely impossible. I do, however, feel that there are a couple of issues that make it easier than it should be. The Berserker's MIGHTY SKIN OF STEEL is one of them, of course, but apart from that, the main problem is line-of-sight kiting. Yes, a well-practised level 6 Berserker will kill a Flesh Pound relatively easily in isolation - but it usually isn't. If the only way to engage a Flesh Pound without enraging it was to charge at it despite unfavourable circumstances, it'd become a lot less appealing very quickly. For all the times that a Berserker can safely engage a Flesh Pound as soon as it appears without assistance, there are five more where it's meatshielding two Sirens and surrounded by Crawlers. Cue the teammates sniping the ranged attackers and covering the Berserker's flanks, because he'd usually need them.
But then we encounter another issue. What if everyone's spread out? The Flesh Pound won't have many minions then, because they'll be thinly spread across the map, so, ironically, not working together would actually make it easier, as a couple of scary ghost's videos demonstrate. Sounds like a job for another suggestion I've been plugging for quite a while: MaxZombiesOnce scaling.
Let's face it - even in today's KF, a decent team will hold off the hordes without much trouble. The game doesn't really "start" until the big specimens arrive. When you have at most 32 specimens between six players, it isn't hard to see why. So what would happen if there were more? I think the whole game would be better off for it - I've always felt that the hordes should be genuinely threatening in their own right - but let's focus on Berserkers for now.
Firstly, having more active specimens would make splitting up much less desirable, as you'd have more threats to deal with on your own, and Flesh Pounds would usually have a bigger and more threatening retinue. Secondly, the scaling would do a lot to combat the last man standing phenomenon, because while Berserkers geared for that style of play can push through hordes to an extent, they don't kill things very quickly (relatively speaking), and having more active specimens saps at the Berserker's most valuable commodity - room to move. Crowd all of his escape routes, and even the best Berserker on the planet can't do much about it.
There are a couple of other rage mechanic changes I'd like to see too, but they're low priority. Currently, when an enraged Flesh Pound attacks, it calms down after the first successful hit. I'd rather that the whole attack was enraged - I'm pretty sure the second punch would hit if the Flesh Pound kept the movement speed bonus, not to mention most of the blender attack, and if so it'd hurt like hell. The other change is that whenever a Flesh Pound is due to calm down, if its TwoSecondDamageTotal meets the RageDamageThreshold, it should simply stay enraged instead of stopping to enrage again. If the team goes for broke with their damage output, so should the Flesh Pound. That might be a bit excessive though - I'd need to see it in action before committing to it. (I do actually plan to make a balance mutator including those changes when I have time, but don't hold your breath - I'm a legendary procrastinator.)