First off, a very good build.

However in long games (50+ mins) it starts sucking and from all sides.
The damage, crits for 600s with 5 items -> buying HP doesnt help even if its a sunfire cape (50 AoE DPS)You just wont have enough HP to live through team fights.

So I was wondering if anyone has a good DPS mundo build with better survivability.
By the way I'm basing myself on a guide I found here, Spirit Visage,Mercury Treads,Phantom Dancer,Starks Fervor, I finish It with infinity edge in long games.Spirit visage and Mercurys Treads give excellent survivability early and mid game due to the effect on his ult but in extensive games I doesnt matter anymore.

Sometimes I play a hybrid which goes: Warmogs Armor,Mercury Treads,Sunfire cape/Thornmail,Atmas Impaler,Infinity Edge,Sunfire Cape.This turns me on a nearly crowd control, high HP/Armor tank with awesome-for-a-tank DPS (crits as hard as the DPS build).
I fill warmogs in long games and is practically invincible in battles as harsh as 3v1.

Late game you're suppose to sell Spirit Visage and get Force of Nature, that along with any good HP item should be more than enough.

http://www.leagueoflegends.com/board...ad.php?t=51570

Build v1, with Guardian Angel or Banshee's Veil as the sixth slot. When complete ~85% Crit Chance, ~1.3 AS, ~140 Armor/Resist, ~45% Dodge, ~470 move speed.

Progresses something like: SV, Ninja, Zeal(PD later), EC, Zeal(PD later), Banshee's then complete the PDs as you can.

Merc's aren't terribly effective with Burning Agony, only gaining an additional ~12% iirc from the thread on the duration reduction from what Burning Agony lists due to them not stacking additively.

Though to be completely honest, it really isn't that build, its the practice with the playstyle and champion that probably needs the help. Think Carry, not Alistar.

In my personal experience at level 18 in long ass 1 hour 30 minute games FoN helped me more than SV.