Orton's triple threat is not random this feud has been hinted at for months, since before 2010, if you ask me it is the least random match.Most WM feuds were long drawn out feuds were when both brands didn't have a PPV every month. Raw's feuds were always great leading into Mania because they didn't have a PPV between the Rumble and Mania. Even SD had great feuds because single brand PPV's didn't really matter, that's why nothing happened mostly at NWO, except Eddie winning the WWE title. HBK and Taker is probably one of the most lengthy feuds going into this Mania. Even though the match was made after EC, this feud has been brewing since the Slammy's which is awesome to have such a long storyline, we don't get that anymore.
As much as I like Cena/Batista, it was pretty much thrown together after EC. Too many title changes and random matches ups heading into Mania for the past couple years. Edge and Jericho should have made a little more sense than it does, Cena/Batista makes way more sense than that crap.
Orton's triple threat and HHH vs. Sheamus are definitely the most random matches at the show.
After analysing the card I am pretty sure, not definate, that WM will be a huge draw and could be one of the best, but knowing the WWE, I'm probably setting myself up for a fall.