I would tend to agree with greendwarf - PHEVs in general (not just the Outlander) are aimed at people whose daily usage is within the average estimated EV only range (though not necessarily only using EV - higher acceleration at junctions might require a bit of engine power) - with the occasional (ie weekend) longer journey where it's going to be using mainly petrol. And by average range, I mean what you actually get, not what the dashboard estimate says. So for older cars like mine, that's around 20 miles/35km per day, newer ones should get more as they've got bigger batteries.
All rechargeable batteries do degrade, and yes, the software on the Outlander may not be getting the best it could from the battery. But I'd also say that petrol and diesel engines also lose efficiency as they age too albeit over a longer time period. Battery powered vehicles have only relatively recently matched petrol/diesel cars in terms of performance and price, so you really shouldn't expect them to have the same levels of longevity yet.
If you do match the PHEV target market then I would say don't worry too much. Compare what's discussed on the other PHEV forums (Audi, VM, BMW, Kia etc) and you'll find much the same. I did a lot of research before I bought mine (very nearly got an Audi A3 etron), and came to the conclusion that the battery will degrade, but probably not enough in the time I intend to own it to cause me any issues. Being sensible and not rapid charging too often and not forcing it into EV mode when it might be better using a bit of petrol will reduce the rate at which it degrades.