In 4th edition, one of the biggest problems I've found with solos is that they get locked down way too easily--between stuns, dazes, immobilization, and other effects...they are far too effective when used on a single enemy threat. On the other hand, I don't want to stop players from using them altogether, by removing any utility of the powers. What tricks have worked to keep these poor, defenseless dragons (for instance) dangerous in your game?