It actually isn't that easy, because Toxicroak is a Poision type and therefore immune to Toxic (obviously). The burning damage is as high as the Dry Skin healing so Jellicent needs to attack in order to beat it. PP Stalling is also possible but Toxicroak can to the same with Swords Dance.
The Jellicents in the Smogon analysis are all OHKOed by this +6 LO Sucker Punch (burned). Even the 252/+252 dies 75% of the times. In this situation you two are pretty much equal - disregarding that Jellicent needs four hits to connect while Toxicroak only needs one.