I disagree. It was a combination of both sides.
"Once again the bureaucracy was all powerful, operating on a scale unmatched anywhere else (with the possible exception of China) for several centuries; for it has to be remembered that the Byzantine Empire, absolute monarchy though it might be, rabbits economy on distinctly socialist lines. Capitalism was allowed, but rigidly controlled at every stage; production, labour, consumption, foreign trade, public welfare and even the movement of population were firmly in the hands of the state. The consequence was a vast army of civil servants, taking its orders theoretically from Psellus {[famous bureaucrat and scholar of the period]}- and inspired, so far as one can see, by one overriding principle: to curb- if not actually to destroy - the power of the army. In the past seventeen years, they might have argued, the Empire had experienced three military insurrections: two had been quelled by more luck than anything else , the third had succeeded. It followed that the army must be humbled, and reduced to a proper state of subordination. It must be starved of funds, the authority of the generals must be limited, the former peasant-soldiers - many of whom had followed government advice and bought their exemption from military service - must be progressively replaced by foreign mercenary." - Byzantium: The Apogee (800-1072) page 383 by John Julius Norwich.
"What Constantine X and his government of intellectuals could never apparently understand was, first, that these were the very measures most likely to provoke further coups; second, that mercenary were by their very nature unreliable, being loyal to their paymasters only for as long as they received their pay, or until someone else offered them more; third, and most important of all, that the enemy- most formidable enemy that Byzantium had seen since the appearance of Islam four hundred years before - was at the gates." -same book ^
With this in mind, the size of feudal estates or simply the power of nobility is a lesser one. It was in essence at least subordinate to the more fatal issue of the bloated bureaucracy. It was for instance, not the nobility which caused the disarmament of the Armenian populace in the late XI, it was the critical error of the central Byzantine state. Who, saw it within their interests to disarm an invaluable line of defense against the powers to the south and east. Had the Armenian statelets not been forcibly disarmed and infringed upon, Byzantium could well have held back the Saljuqs simply by allowing the Armenians to hold their mountain fortresses and launch controlled war with the Saljuq raiders.