Well, basically... compared to canon (particular the 4th and 5th Grail War) Berserkers, he has no stunning offensive ability, nor matching defences.
On a one-by-one basis:
Lancelot still retains fighting ability. This, on its own, is enough to get him out of trouble. On top of that, his armour is enough to survive being run over by Gordius Wheel, or hit several times by Gate of Babylon projectiles.
Bersercules has the near-invulnerability by God Hand, insane speed and strength... and residual ability left by Eye of the Mind, making him hard to feint. Definitely a nightmare; in this war, the only way to take him out would be to hit him with Arondight, a horse, and then hope Archer could get in a good shot.
Fate/Extra Berserkers: Amongst other things, the war format helps protect them from what would otherwise be a very sorry circumstance; it all comes down to straight one-on-one fights. Still, Lu Bu has frankly insane stats, armour, and a semi-functional transforming weapon NP. Arcueid... is a True Ancestor, and even nerfed she's not wholly incompetent.
Apocrypha: I'm not so sure, but Frankie seems to be relatively sane, plus has odd NP's, and a useful skill. The Great Grey Gimp is basically a walking tank from the wiki descriptions. Kintoki, in the cancelled project, is just childish.
The problem is that you've got a Berserker with all the crazy insanity of Heracles, without any of the defences, anything to attack with, or much compensation other than 'sheer raw strength'. If he hits, the damage would be enormous--but he's not fast enough to make simply 'getting near' a dangerous prospect. I think Samson killed a guy with a bone, which might be a start.
Unrelated, since this is taking a while and I have an idea, would you have any objection if I start off the IC posting and summon Lancer? XD