tl;dr version: slots placed after 30 still count, so yes, there is a reason to level past 30.
Long version: Unlike for powers, the game can't tell when you placed a slot, so it can't deny access to only some of them based on what level you placed them at. Also, *you* don't have any way of telling which slot was placed at which level, so you wouldn't be able to know which slots to put enhancements in and which not to (say you have 6 slots in an attack, 2 of which you placed at 31. You can't tell which is which just by looking at them). So, the game just lets you keep the slots placed above level 30, even though you are exemped down. However, you don't keep the *powers* you placed above 30, and I don't know for sure if you keep set bonuses from sets slotted in powers you lose access to. But you definitely get set bonuses from the rest of your sets, as long as the enhancements aren't more than 3 levels above the level you're exemped to (so level 33 or less in the case of siren's).
Also, might as well level to 50 eventually just in case you want to play in RV at some point - perhaps when SC is empty, or whatever. Also, being level 50 lets you slot purples if you can afford them, which are both massively powerful and unique in that their set bonuses work while exemped even though they're level 50.
tl;dr version: slots placed after 30 still count, so yes, there is a reason to level past 30.
Long version: Unlike for powers, the game can't tell when you placed a slot, so it can't deny access to only some of them based on what level you placed them at. Also, *you* don't have any way of telling which slot was placed at which level, so you wouldn't be able to know which slots to put enhancements in and which not to (say you have 6 slots in an attack, 2 of which you placed at 31. You can't tell which is which just by looking at them). So, the game just lets you keep the slots placed above level 30, even though you are exemped down. However, you don't keep the *powers* you placed above 30, and I don't know for sure if you keep set bonuses from sets slotted in powers you lose access to. But you definitely get set bonuses from the rest of your sets, as long as the enhancements aren't more than 3 levels above the level you're exemped to (so level 33 or less in the case of siren's).
Also, might as well level to 50 eventually just in case you want to play in RV at some point - perhaps when SC is empty, or whatever. Also, being level 50 lets you slot purples if you can afford them, which are both massively powerful and unique in that their set bonuses work while exemped even though they're level 50.
@MuonNeutrino
Student, Gamer, Altaholic, and future Astronomer.
This is what it means to be a tank!