If you think about it, even in the classic series the regenerations go more violent gradually with Baker-McCoy and McCoy-McGann in mind. For the classic series anyway, those two were ever so slightly more violent than previous ones.
Hartnel to Troughton: He just lied there and quickly morphed.
Troughton to Pertwee: Well in the war games we didn't exactly see the actual transformation, but he did spin around a bit then stumble out the TARDIS in Spearhead. But if you take the fan film "Devious" as cannon as it actually had Pertwee in it, then there was a bit of suffering in it, but that's after the regeneration and when the timelords whipped the Doctor's memory. Nonetheless, ever so slightly more violent, although not really that violent anyway.
Pertwee to Baker: Really non violent again. A few tears and needed to be triggered off to start, but the actual transformation really was not violent either.
Baker to Davison: Probably a tad more violent than previous regeneration with the watcher sort of walking into the Doctor, but not really violent either. In a way, more peaceful.
Davison to Baker: Now this is where the violence rises. A haunting scene of memories about Andric and the Master. Plus is the first time the slightest sign of glowing light was seen at all (although I haven't seen Caves of Androzani in full, just the actual regeneration scene).
Baker to McCoy: Here's where we see the first slight resemblance to modern regeneration. Although the Doctor was lying down, we did see some light emerge from his face albeit multi-coloured as opposed to flame colour. Now this is where it begins getting more violent.
McCoy to McGann: This time the doctor actually properly morphs. It looked uncomfortable and slightly more violent than previous regenerations.
McGann to Hurt: The first stand up flame regeneration. McGann illuminates then a quiet but blinding explosion is seen. Slightly more violent again.
Hurt to Eccleston: Unfortunately we only see the beginning of this regeneration but I predict it probably was the same or similar to Eccleston's.
Eccleston to Tennant: more violent than previous ones yet again with the doctor bursting into flames then morphing.
Tennant to Smith: The first very violent regeneration, the TARDIS actually explodes along with the doctor.
So who knows what will happen with Smith. Will the he explode again? Or will we go back to a more traditional regeneration? (I hope not) Rumours have it this time the doctor will actually hover when regeneration as I heard something about Smith receiving and injury when being lifted to a harness in the regeneration scene. Would be fun.