There's a lot going on here that can be fixed next time you make this:
1) Check the crush -- it's the number one reason for poor extract efficiency. Folks say you need to "crush until you're scared" of it becoming pure flour which is impossible to sparge -- that's pretty much what I do. But, like Denny says, with that grain bill you'd still have had to get around 100% efficiency to hit your planned OG. So in that case...
2) You didn't sparge enough or boil enough. It takes a lot of sparge water to rinse all the sugars out of that much grain, and it takes a lot of time to boil all that extra sparge water down. Next time, sparge enough to plan for at least a 105-minute boil -- that's what I do for Scotch ale. Two full hours or more would be even better if you don't mind the "waste" of time and energy.
3) 155 F is too high of a rest temperature. If you want a high gravity beer to finish at anything other than a relatively high final gravity, you need to keep that mash temperature down to 150 F or even lower.
4) You used too much crystal malt. Crystal malt has a lot of unfermentable sugar. Bring that down to maybe half as much and you'll be in better shape.
5) Not enough yeast. With a really big beer, you need to make a really big yeast starter. Pitching straight unstarted vials is never a great idea, but especially so with big beers.
Fix those five things, and I can virtually guarantee your success in the future.