The only doubt I have about Bullard rests in the fact he's injury prone. In every other respect regarding what we need from a central midfielder, Bullard would improve this club.
To say he's not much better than Osman, if that is truly the case (I doubt Osman could have the same influence on the right at a Fulham that Bullard exerted last season in limited play.), doesn't matter. We need a central midfielder who can create and complete a pass to someone wearing an Everton shirt on a consistent basis. Bullard has routinely done that work for his clubs in his career. We certainly could've used that ability last weekend.
£3-4 million for Bullard is a good deal and would at least fill that gap that was so obvious against Blackburn.
But if you sign him, you are always taking a risk that he will not last even 2/3rds of a season. Considering the injuries, can you risk adding someone with such a history? Considering the available personnel in the centre midfield, can you afford not to take the chance?