The new poison system that's being implemented in Mists of Pandaria might seem like a fairly major revamp for a class that's typically seen very little change between expansions. The conversion of poisons from items to skills and the new lethal/non-lethal categorization is a massive update compared to what we saw between Wrath and Cataclysm. A rogue's ability to provide utility in a raid environment is being expanded dramatically and has always been a weakness of ours.
The truth is that those changes pale in comparison to the other poison updates due in Mists. While not carrying poisons around in our bags is simply a quality of life change, obtaining new poisons for the first time in years will have a much larger impact. The poison crit system, which has been fundamentally flawed since its inception, is being redone properly. Shiv is actually going to be back on every rogue's hotbar. Poisoning both weapons at once is merely chump change, while the rebirth of random stuns deserves the loudest possible heralding.