I wonder where these expectations come from? Since we last won the league, we've had a couple of decent 2nd place finishes, other than that we've generally been around the top 8, but also had a relegation and a few low-mid table finishes. O'Neill, by Villa's recent standards, is doing an above average job. Then consider that he's also come to us in the era where any team not playing regular champions league football is massively handicapped from the off, so I'd say he's doing a great job.
I can't remember too much of the football we played before Taylor's first reign, and I was too young to make a judgment on it anyway. But apart from Big Ron's team, most of the recent sides have played some pretty dire stuff a lot of the time - DOL was the worst I've seen, Gregory and Little's sides were great on their day but too often sent me to sleep and both really struggled to score goals. My enduring memory is endless low scoring draws. By Villa standards, I'd say O'Neill's team fit right into expectations.
Basically, based on the size of our club and resources and the current benefits enjoyed by the CL clubs, I would expect Villa to be competing regularly in the top 8, anything better would be something special. I don't agree with everything he does, but I think O'Neill is doing as well as can be expected.