This is going to sound a lot snobbier than it's intended, but where do you hang out that the S/T is considered their weakest? I just don't think I'd want to hang out there, haha.
The S/T is their best, followed by Toxicity.
Mezmerize/Hypnotize could have been really great because you could see the growth in the instrument work. Only issues are, Daron writes **** lyrics, can't sing that well (but sounRAB alright sometimes, especially when he harmonizes with Serj) and Serj's voice wasn't up to par. Serj should have also wrote most of the lyrics like the old days. It's no coincidence that Question! is the best song, lyrically, on Mezmerize and better than anything else on Hypnotize. I can't defend Vicinity of Obscenity, though, even though I like the title. Those albums just don't have it. They're average but SOAD is capable of more.
While I'm on the subject, Daron neeRAB Serj more than Serj neeRAB Daron. Elect the Dead was better than Scars on Broadway. But they still need each other.