In theory it is pretty good but there's a problem...
Deadly Poison isn't played anymore in Rogue lists.
Wacking enemy minions especially during late game is suicide when we don't have any healing. So that card is another bust and won't see play.
Right I agree, it probably wouldn't see play in the current only viable rogue deck, but it's at least a pretty good card that could have started something, had they worked on making rogue something, instead of just slapping a few stealth tags on stuff and call it unique. Rogue is poorly designed overall, it has an over reliance on weapons, down to the hero power, but no way to actually use weapons effectively anymore(rip blade flurry hit+board clear+nuke). It doesn't have healing and I guess thematically, it makes sense, and it doesn't have taunts(which are only partly good for that but still) and again that makes sense thematically.
I think what they needed and I believe someone here mentionned it before is more poisons, to make the weapons not shit. Deadly poison is good for a pure damage oriented, but you'd also need like a poison to make it like that hunter weap that does damage without taking damage in return, that'd make a lot of weapons really viable again for rogue. Freezing poison to prevent shit from attacking. Corroding poison, gives the weapon +5 but destroys it at the end of the turn. Mind Steal poison, when you attack, Draw a card(or steal a card whatever, helps with draws which is another point where rogue sucks, auctioneer nonsense aside). Then build on that, make pirates more relevant for rogue since they have the weapon synergy usually, make spells that affect weapons, example Shadow Clone, For this turn, if you attack with an equipped weapon, deal the same damage to 1 random enemy Combo 2random enemies. Or like Blinding Speed, for this turn, attack twice with the weapon, combo, 3times.
Problem being, with the lack of poisons in vanilla, you'd kinda have to re-add poisons every expansions after a new season or whatever they call it, when they rotate out old shit. And it's kinda late to build on that now for this round.
Stealth just feels like a poor idea to build on, especially since, given enough buffs to it, what you'll end up with is a rogue playing a bunch of shit you can barely interact with, buffing them a bunch, and killing you in one turn. And surely they don't think that's a good fucking idea, but that's the way stealth works, it lets you do that shit. Or you could do a always face rush deck if there were enough stealth minions, where you basically ignore everything else and try to race the opponent, but without the hunter hero power I don't think that's such a great idea. But god that's fucking boring, even if it ends up being a thing.