I know a couple of guys like this. They have great sprints but almost always get dropped mid ride (training rides at race speeds). Here's my recommendation.
(1) Get the to front. It is too easy to sit in on group rides. Take your pulls and do them often. Attack during the rides (without being a jerk). You have to hammer yourself (to a reasonable extent) while training to keep up with the big guns IMHO.
Also, don't get to caught up on the number of hours or miles. It's really the quality that matters. I get in about 1-2 hours a day, 3 days a week, plus another 4 to 6 hours on the weekend and I can usually hang with mid-lower end CAT 3s in our area. But, when I ride, it is with a purpose; either to hammer or to recover.
(2) Make sure to go after the intermediate and town line sprints during the training rides if you can. If the group doesn't do them, try hard break away efforts at times. These all out efforts are great for building peak power.
Hill/power intervals are also great for buidling power for these peak efforts.
(3) Depending upon where you are getting dropped, there are perhaps other things you can do. If on the hills, try to drop some body and bike weight if you can. If it is the high speed efforts (27 to 30 + mph) where you get clipped, check your gearing (a 53 x 11 is a must for our rides during summer). Aero wheels can also make a real difference. I picked up a set of Spinergy Stealth Carbon PBO wheels last year that gave me about a 1 - 3 mph advantage over conventional wheels. That doesn't sound like much, but it is the difference between hanging on during these hard efforts and being left for dead off the back.
(4) Try to pay attention to when the hard charges will come. I know a number of guys who love to stomp as soon as I come off a hard pull. (No deed goes unpunished....) So, I make sure that they are midway through a rotation from me, or I cut my pulls back a little when they seem frisky to keep from having them hammer me during such a time of short term recovery need.
(5) I think the biggest mistake a lot of riders is they don't eat and drink enough. If this is happening mostly in the last 1/2 or 1/4 of the ride, you may find that eating and drinking a bit more will help you to maintain your power longer. Cytomax is my personal favorite drink as it prevents lactic acid cramping.
One person's opinion. Good luck.