I have done several AEG projects where I was able to get 1-2fps fluctuations. The key is really to take your time and put a lot of attention into the compression. Particularly in the hop-up chamber, and between the nozzle and bucking, much overlooked parts.
On a side note about FPS fluctuations, I find it has a lot to do with the ammo you are using. Lesser ammo always seems to be less velocity consistent, which may be why our bolties have that reputation for consistency. We pretty much always use either very heavy (where the fluctuations are less pronounced) and/or top-of-the-line quality ammo. Most AEGs users use average .2g and .25g bbs. If I run SGMs in my AEG, and keep the rate of fire down, I can achieve bolt-action level velocity consistency. By the same nature, using Matrix .2s in my VSR would get me the typical AEG fluctuations.
That is not to say that just by using nice ammo you'll have a perfectly consistent AEG, or bolt action for that matter. Only that it may be contributing to the stereotype that AEGs are just outright less consistent. In either case, time and care must be taken to get consistent velocity. Although I will say that I find it considerably easier to get really good consistency in a bolt action than an AEG, simply because of the nature of the way the nozzle works in an AEG as opposed to a bolt action.
However, I do believe bolt actions are more consistent in one regard. In AEGs, the tappet plate is released and the nozzle springs forward and slams the bb into the hop-up chamber. In a bolt action, we can chamber the bb in a much slower, more controlled manner. This means more consistency in the starting point in the bb and thus in the spin applied by the hop-up. It is a pretty minor thing though, and newer designs like the G-hop and R-hop by the nature of their much greater contact area should essentially negate this.
As for DMR vs bolt action in general, the answer in my opinion is that it simply depends on the application.
Bolt actions are quiet and highly precise guns. They enable the user to stealthily take accurate shots at targets a long distance away. They are for those for whom rate of fire means little; volume of fire is traded in favor of staying hidden. These players are looking to play primarily a recon role, and take shots generally at high value targets or targets of great opportunity without being detected. For them, the bolt action suits the style of playing very well. A DMR accurate for sure, and effective at placing larger volumes of precise shots downrange, AEGs tend to be quite loud, which compromises the location of the shooter. And in practice, the shooter would often get discovered, and be forced to rely on that rate of fire to escape.
Where the DMR proves more practical is in the hands of well, a DM, for whom they are designed. If you are playing a support role, and your job is to keep heads down from a distance using precise shots, the inability to fire in relatively quick succession proves ineffective. Stealth is far less of a priority. To a certain extent, the shooter needs to be able to put a decently sized volume of fire downrange, and need to do so far more quickly than a bolt action would allow. No heads will be kept down when you have to manually chamber a new round each shot. To that end, the semi-automatic DMR is far more effective in this scenario.
So essentially, it depends on the application. The bolt action sniper rifles are for the snipers, and the DMRs are for the DMs.