Personally, I'd use a d10 instead of a 2d6 system.
I have it on what I consider to be good authority (an ex-GDW employee) that throughout the development process, MT was meant to use 1d10 for task resolution, not 2d6. At the 12th hour, a decision was made to stick with 2d6 instead, because that's what Traveller players would expect. All instances of 1d10 were changed to 2d6, but nothing else was altered. The result was task profiles that didn't make sense. The printed difficulty numbers are quite a bit more reasonable when viewed through the lens of d10 probability.
For 2d6, the standard target numbers should be
Simple: 5
Routine: 8
Difficult: 11
Formidable: 14
With 2d6, the probabilities in that progression are very close to what they would be in the printed targets of 3, 7, 11, 15 if you were rolling 1d10 instead. I've played it this way for years (with 2d6) and found that it works superbly. Or you could use the task profiles as printed but substitute 1d10 wherever the rules state 2d6 (essentially reversing the last-minute "change all" that caused the confusion in the first place). IMO, the decision to stick with 2d6 as emblematic of Traveller was a good call; making that decision as the boards were going to the printer, without time to implement it thoroughly, was quite unfortunate.
I wrote an article on this some years ago and posted it here, if anyone's interested in a more in-depth discussion --
http://home.comcast.net/~s.winter/traveller_tasks.htm
Steve