Hi there.
Believe it or not, there are still reasons to grab and throw characters with Sheik in v3.6(beta). Down Throw is still a pretty strong throw for position and still allows for re-grabs because of how strong/long her boost grab is as well as dash attacks which are a pretty staple launcher. In addition, if characters are forced to tech --- because of the way that teching works in this game (it does not conserve your momentum into the tech roll), it is actually easier to tech chase characters across the board. A very easily observable victim of this is Bowser, who has some of the easiest techs to catch in the game.
If someone DI's incorrectly, you are still able to follow up with aerials such as fair or nair or etc, but the primary goal of Sheik (like in Melee) is to stretch the knockdown and choke out positioning from opposing characters. There are a myriad of ways to accomplish various things post the knockdown or off of poor DI choice. DSmash, Dair, DACUS, boost USmash, Ftilt, Dtilt, Utilt, Fsmash and the aforementioned dash attack are all moves that launch characters upwards or outwards into the rest of her aerial game.
As far as the reasoning behind the change of B-Throw/D-Throw, both of the throws had the exact same stats: 8 Damage, Angle of 62, 70 BKB and 55 KBG, however both of them had different release points. Down Throw released closer to her and further away and Back Throw released higher and farther away... but you could act sooner from it. What this meant is that for most characters, not only were you able to do all of the things that I mentioned in the previous paragraph (various launchers, tech chase, etc), but it also enabled those "Oops, I died." guess scenarios with DACUS/fair/nair that many opposing players were forced into.
While I would probably agree that Sheik has lost some of the fun quotient that the mixup had, I don't think the assertion that "there is no reason to throw" or that "there is no point in grabbing" is valid. If you feel like there is a more interesting character for you to play now, that's unfortunate, but I wish ya'll the best. I'll still be sticking it out with Sheik for the most part though and seeing what I can learn. I think that she is still a strong character in this version and I have fun playing her.
As far as other 50/50 guess scenarios go, even if they might not have been changed currently, we are looking into those and coming up with ways to address things like that. A lot of characters get changes between every version of the game. If we don't change something at a certain time, it generally means that we aren't confident in a solution or maybe it's not something that has been presented as a problem. We have to look at things in a broad light in development so sometimes things won't always work out immediately.
#pleaseunderstand