I'm on my 5th Avensis (all company cars) in the last 13 years and have covered approx 500,000 miles in them.
All diesels and the only problem I have had with any of them was with a 2008, 2.2 litre saloon, as already said there was an issue with that particular engine (also used in the Lexus 220d).
Never had a Volvo but their reputation is legendary, but the Avensis appears to be "Bullitproof", only problem for me is this will probably be my last Avensis the salesman told me that production is to stop and there are no plans for a replacement.