I don't think it's technique or his putter. It's a mental issue - belief and confidence - and the only way he's going to change that is by holing more putts.
A vicious, or virtuous circle depending.....
A fairly incisive observation. At the moment McIlroy is bereft of any degree of confidence and that has to filter through the rest of the game. Look at how Spieth holed out for the majority of the Masters. It meant he could play with confidence and trust himself to save par. Same with Willett. He made a few good birdie and par putts on Saturday and suddenly had belief on the greens which let him go for the shots