Hmmm...The limit should be the usual 2,147,483,647. I guess I can implement a protection against it (never thought someone will hit it!)
I'm not sure if the lag has something to do with dancer, dragoon, or just having too many traits & buffs in the game. With how the game is coded, everytime a status (including an instance of +stats) is added, it'll check all other status on that follower to see if something special is happening. So with a dancer duelist setup, the duelist will end up with A LOT of status on them and will make sbsequence attacks talking exponentially more processing power. I don't know if you are playing on browser or standalone, but I think standalone should be able to mitigate this lag way better.
I can't think of a reason for why duelist will not work as intended with large numbers or why it'll randomly die without overflow tho. I'll try the setup myself later.