That's definitely a contending team in my league. In fact, I'm surprised you managed to snag that combination.
You're right in that your D-men are the only semi-weak link, but they're not so bad either. Doughty could easily be a top 5 D-man, and Pietrangelo will keep your +/- high all while contributing some decent numbers as well.
I'm not a huge fan of Vanek personally. I know he had a good start last year, but he wasn't able to sustain it, and I have a feeling it won't carry through this whole season either. Some people seem to like him a lot though, so you may be able to beef up your defense by trading him out. Havlat is hit or miss as well, so maybe a combo of those two could give you a solid D-man in return.