The only time I feel weak is when I shove my body into their face, then wonder why it didn't do any damage Xd
Being more of a mage player though, this is an uncommon occurrence since I prefer staying back and sling spells from a distance.
I think, if they really want her balanced:
One idea I had in mind, if Riot is that desperate to keep her waveclear intact, is to only allow Sigil's damage onto the bounces. Not sure how viable this is, though. Looks terrible as you become extremely dependent on AP to waveclear. Looks atrocious late-game Xd Probably better to just remove the waveclear aspect on her Q.
Remove E's ability to proc the passive.
Allow her passive to do reduced damage if procced early, scaling up from 0 - x damage over 0 - y seconds. This helps smooth out her damage output, will make every other LB happy, and is relatively easy to balance. This also eliminates that forced high-damage proc that is used as compensation for the delay.