His weaknesses are huge, and his strengths aren't. There are way too many cards that flat out own Dreadlash, and only a handful of cards that Dreadlash holds an advantage over
Min 5 makes him suck hard vs staples like Nellie, Edwin, etc
4 damage is puny and not scary at all, any dr or defeat: +life easily negates him
He is weak vs any attack manip clan. He is weak vs All Stars. He is weak vs soa. By weak I mean he doesn't really have a huge advantage over any of these..
Add to the fact that you have to play a certain way to properly activate his ability and match him up vs the cards in your opponents hand that are actually susceptible to him ... This is why you almost never run across Dreadlash in elo...
I'll make a different comment than the ones i've seen so far in this thread. i'd go with Dreadlash actually, he is like a Pilzken (yeah yeah he only has 4 dmg). i'd probably go with a high damage deck so that in the 1st/2nd round i'd 'atack' with a high damage card (when you had them ofc) and then you could try the ko with Dreadlash or just leave the opponent with 2 or 3 life, if you didn't have the pillz to finish the opponent off. i prefer Dreadlash because even though he doesn't have a lot of advantages against quite a lot of cards, the factor surprise is also really important and believe me, most people wouldn't even think that you can try to ko with him if he doesn't have his power active, for example (and the ones who do, keep in mind that the bonus is pretty helpful in k.o situations)