I'm not a fan of Mercedes because, while their overall number of repair trips doesn't seem all that high (see the data on this site) they're just so darn expensive to work on when they do develop a problem, and even when they don't. Price out prepaid maintenance on a Mercedes and you'll find that it's just about the most expensive of any car out there. You should youtube scotty kilmers short video on Mercedes.
Ultimately it depends what you're looking for. In terms of function and driving dynamics, a Mazda 6 will do basically what the CLA will do but without the nameplate and without some of the bells and whistles. And it will last longer, cost less upfront, and cost a fraction in terms of maintenance. For a luxury name, the Infiniti G35 (used) and Acura TSX are luxury cars that are actually reliable.
If you're dead set on European luxury, you can kind of pick you poison among each maker's entry level car - the BMW 320i, the Volvo S60, the Audi A3, etc. They all have little strengths and weaknesses, but in terms of their overall quality as cars and their costs of ownership, they should all be roughly comparable. Mercedes made their advertising push a year ago or so saying they had got the CLA under $30k, but everyone else isn't much over that number anyway.