I'd imagine he must have purchased a bunch of graveyard upgrades at the citadel to respawn faster.  This does bring up a very serious issue.  Aside from trying to intercept him some distance from the citadel, I don't see a good way to stop this in a 2v2.

Building hit point upgrades are actually a very good investment, since towers cannot be replaced.  Having a mostly intact tower line in the late game can be extremely rewarding, and I have come to agree with others that one player must purchase the first level of building hit points when the game begins.

Maybe he shouldn't be able to target buildings while in last stand mode

Well to be fair... although Oak may excel at Fortress because of this, UB has a clear, dare I say it.... OP advantage in Domination. It works like this. Pick any character you want. Play Domination and verse all UB players. Now, watch as the UBs get to the flag before you do, creep before you do, and when you do fight them.... He'll kill you. No one is as effective in early game as UB simply because of spit. Since you are deprived of exp, the characters that can kick Ubs ass mid-late game, simply can't because Ub controls map. Harass, harass, harass.... and stay near flags. Boom. Insta win.

Is it possible to stun Oak whilst in Last Stand?

Reducing overall damage of last stand would be just plain stupid, as it is it's only purpose.

Agreed transitive. Regardless of game type. The first upgrade needs to be bought. In fortress, they are mandatory. In that mode the fortresses can be viewed as your health. Dont you want your health to regen?

I bought the first level.  Don't the rest of them just give like +5 regen and +300 HP or something?  They were utterly useless in beta, but maybe I missed a buff.

About the other demigods: the thing is, I can actually defend against them by, y'know, hunting them down and killing them, setting up observer wards and intercepting them before they reach the fortress, or scaring them away while the fortress regenerates.  Oak can just ignore me and still wipe out my fortresses.  This guy wasn't even doing it as well as he could have: he should have shielded himself on the way in to make sure he got there and did maximal damage before dying.  I also don't think he had as many points in Shield as his level allowed -- that would make this even more effective.

The problem was, we had to push the traditional way, where you don't, you know, die.  That means we had to take out all the towers in front of and around the fortress first, and deal with defending demigods.  He just ignored everything.  I will admit that we had let some of our front defenses go, because we had trouble early on and because I didn't anticipate this strategy -- when it was 2 fortresses to 2, we were dominating the map to the point that we could defend fortresses easily, until he got Last Stand.  I don't think it would have mattered.  He would have ignored them the same way he ignored us when we jumped him on his way out of his base.  (and if he'd been smarter, he would have approached the fortress with his shield up)

Anyway, I'll see if this happens next time I'm up against Oak, or if I was just dumb.  I guess the smart money is on the second option there.

Probably the best counter is to buy lots of structure health (except I still think that's useless...I'll have to look at the stats in-game), and to just concentrate on knocking down his fortresses.  I think our biggest mistake was that we tried to defend; once your opponent does this you have no choice but to attack as fast as possible.

lambdaman,

fortress upgrades beyond the first continue to add health on a percentage basis. each upgrade provides a further +10% to max health. regeneration rate is also boosted by a large amount, though you may be correct that its a constant rate. regardless, the scaling on it is not small but is large. with 3 upgrades to building health i was able to see my fortresses have 18500 health and regenerate about 3000 health in a minute. 

It sure is!

Stun him, distract him, slow him down, whatever. I agree this should be looked into however, but I don't think the solution is to nerf Last Stand, since it works as intended.

 However, if we are going to talk about this, which only happens on one game mode, we should also be talking about Erebus curcible map exploit. Both are similar in that they are only effective on one mode/map.

I know that Boulder Roll works to stun him during last stand.