The ranged attack of jellies is fine. It isn't too difficult to dodge, or too rangy, or deal too much damage...
HOWEVER, I think it would be a huge gameplay improvement to make it so that it works like other "directed attacks." That is, it should have a directional attack indicator, and not the generic circular one. Right now it sometimes feels very random whether you get hit or not by them, because jellies have no face, so we cannot tell what direction they are facing.
Feedback?
You'll notice that when they use this attack, the ground under the target breaks and there's a sound effect just before the spike pops up. Personally I just stay mobile whenever there are jellies around, and this isn't an issue.