There's pros and cons either way you do it.
Personally, I prefer the current way. Having a mosh pit is a small price to pay to get rid of bullshit fog of war snipes and stealth champs sneaking the last hit. In addition, teams have vastly more control over who exactly gets the buff by having candidates stand in the circle and the rest stand back. I find it also promotes better team comps, since picking a team that can't wade into the mosh pit is a huge disadvantage when it comes to taking the buff but still retain their natural advantage of being able to constantly interrupt a point capture at range. (Sometimes getting the team to put together a proper frontline is like pulling teeth)
And it's not like mages and marksmen don't absolutely love having the enemy team group up in a tiny circle for them. AoE mages like Brand and Annie have a field day if they play smart and save their CDs until after Xerath is brought down and ADCs can stay safe outside the circle since they can fire into it without worry of the enemy leaving it for fear of the buff being stolen. A Koggles or Jinx that doesn't have to kite can easily delete three or four champs between Xerath biting the dust and the buff becoming claimable.
Finally, the mosh pit can make it harder to claim the buff if both teams are there in force; giving both sides an equal shot at it. It's not a "Let's see who last hits" stand off, but instead forces a team to invest in a teamfight if they want to claim the objective. I've even had one game where the mosh pit lasted so long the buff timed out and neither team got it. It was quite the epic battle, and one that probably wouldn't have happened if both teams hadn't been together in an open field to fight for a major advantage they both wanted.
buff in the middle away from whoever last hits it to whoever wins a "last man standing" battle over a few seconds.
have on this mode, and makes it even more difficult for AP casters (and ADCs) to get access to the buff. **
cant snipe the buff now. But do you expect her to run into that tiny circle occupied by 
etc while she is limited by cds?
