Her DPS is pretty good now. Had no problem taking on a pretty OK Valkyrie on the same lane (tried the new 3vs3 map). Her new ultimate is pretty nice too, since it reveals the target pretty much all the time, making her very nice versus stealth heroes. The damage her ultimate deals is probably a bit to much though, since it has the potential to deal 1500 physical damage at lv 16 if the spiderling gets to hit 6 times. At lv 6 it has the potential to deal 450 damage, which is MORE than pyromancers ulti... allthough you have to keep in mind that it's physical and not magical damage... but the cooldown is like 30 seconds or something :P
I'm pretty sure they're going to be needing to nerf her ultimate damage next patch. It will need to have it's damage reduced drastically. All it needs to do is slow and reveal the target and last long enough to allow Arachna to keep chasing or to run away from battle. I see it more as an ablilty to chase or to run away, than a damage dealing ability, because Arachna has enough damage bonus and agility gain + farming power to deal enough damage without any "nuke" skills.