We have a similar issue here, my 2 year old has a tendency to grab and tackle and lay on top of her siblings. I have seen her pull hair, grab her brother and sister around the neck and pull them down, and drag her big brother across the floor by his hood (that was a several months ago). She can be really rough. And usually she's not angry when it happens. She's playing or she's trying to get something they have, and sometimes I'm not sure exactly what is going on (though I suspect, like you, that she has just sort of reached the end of her ability to play with them gently and needs a break). So here's what we're doing: we are keeping a close eye on her and intervening to either prevent it entirely or to stop it right away. Once we have physically intervened (and given any necessary comfort to whomever she grabbed) we point out that what she did hurt her sibling and remind her to touch people gently. (Then if she's grabbing b/c she wants something, she'll say it and we'll help her solve the problem.) That's it, that's all we do, and the problem seems to be decreasing in frequency. (And if it seems that the little one is grabbing b/c she's tired and just all done playing, can't play gently anymore, then we move her out of the situation entirely-usually by offering a cuddle or a story or something else fun to do.)
For the siblings, we are trying to ensure that they have some private time and space-time to play without being disturbed (and grabbed) by baby. This means entertaining baby while they play. If it's something the older kids want to do with me and dh isn't home to entertain baby, then we include baby.