While we were raiding tonight our guilds hunters and warriors found that they were able to continually have execute and kill shot up.
They did this by:
1. Targeting one of the princes which was not the main dps target. Execute and killshot becames usable.
2. Switch back to the main dps target. Execute and killshot were still usable.
After doing that they found that they would then be able to spam execute and kill shot on the dps target prince until the next switch. By repeating that on the target switch they were able to get kill shots and executes contantly from 100% to kill. If you are a hunter or warrior try this and see if you can get the same results, it's a rediculous dps boost for you if you can get the same results because it's worth it if it works for you.