Both front sprockets have broken teeth. The dealer replaced both with no labor charge, but indicated they would submit a warranty claim to Hobie, but that he was not optimistic.
To my knowledge there are no parts exclusions on the Drive warranty.
The chains slip when trying to sprint with the Mirage Drives. The dealer called it "abusive pedaling".
First time I've heard that one and I'd have to say it sounds like a bunch of nonsense invented by your dealer. A group of us here sprint our kayaks often in short races and adrenalized wake rides. Additionally, some of us participate in formal races and there is certainly no holding back! For all the Mirage Drive parts I've broken over the years, I've never had a cog fail.
During the past couple of years I've noticed some of the chains pinching the cogs, resulting in the chains only partially seating on the sprockets. It can be hard to spot with the sprocket guards on, but is more noticeable in the following picture. You can see the chain is installed correctly, but is partially lifted and will not seat on one of the cogs. If pressed in with a plier it pops right out when the pressure is released. This puts additional stress on the remaining cogs and can very easily be your culprit.
The remedy is usually found by replacing either the sprocket or cable. It is easy enough to pre-test the fit before assembly.
The other less distinct possibility is that of getting air bubbles infused in the sprocket cogs during molding. Though not common, this can happen and is sometimes visible looking through the main sprocket shaft.
In either case these would be considered factory defects not "abusive pedaling".
The tension on the drives was set by the factory and checked by the dealer. Seems unlikely that tension is an issue. Are the Mirage Drives just not designed for sprinting?
It is good to remember that the Mirage Drives are hand built at the factory and subject to variation in setting depending on the final assembler, time of day, etc. Additionally, some dealers are no doubt quite good at making adjustments to the Drives if a problem is brought to their attention, while other dealers don't have the slightest idea how to adjust a Drive. You can go to the FAQ here and verify the correct set-up of your Drive.