It'd be certainly be fun if stealth was a meaningful aspect of gameplay. There are quite a few things they could do with it. Have it provide some sort of bonus while you're not attacking, such as passive movement speed up unless damage is taken, or 10% damage reduction. This would make it worth toggling during movement phases. Then do something like your first hit out of stealth is an auto crit or provides a short damage buff for when you get back on the boss. They could even just give it a simple aggro dump. Anything would be better than it is now. It's not even on my bars and I can't remember the last time I used it, which is a shame.