It used to be that Rogue cards were hyperefficient if you triggered their "special conditions", but it seems that's not true of the new batch. Iron Sensei is trash if you don't activate it at least once and even then, it's not game winning or anything. Cogwrench has a similar problem. Tinkmaster's Oil is way overcosted UNLESS you hit that dream setup. Only Sabotage is reasonably costed, but considering the quality of Deathrattles, kill effects are far worse than transformation.
Everything points to them being scared shitless of creating another dominant Rogue deck like classic Miracle, or alpha Rogue.
It's funny that minion destruction used to be heavily punished cost-wise, because they wanted to avoid MTG style B/x control, but after the escalation of Deathrattle effects creature destruction is now irrevocably worse than creature transformation, making Hex and Polymorph far, far better than Assassinate.