Good rebuttals all, dragharrow. I'm not convinced, but I haven't anything else to bring forth.
Also, Seswatha at least claimed that touching the Heart to receive the Gnosis was a temporary measure. Akka says that they are only supposed to guard the Gnosis until the Consult returns. Then they're supposed to distribute their weaponry freely. I could totally see that being a lie told by Seswatha but I had assumed that the reason the Gnosis was still not being distributed freely was a choice by Kellhus.
If thats true (I don't remember that being said), then it may point to either Kellhus or the Mandate not wanting the gnosis to be free. Like you said, probably Kellhus, but even without him I'd say it wouldnt be released. Men guard nothing so jealously as power.
Also, it does point out that maybe Seswatha did care for the World.
Look at Akka. When he was kidnapped by the scarlet spires and tortured, he leaned on the dreams to get through it. He had already been trained for that situation and was unphased. The same will happen when the first mage battles start. The other mages will be unprepared and they will fold. The mandate will follow Kellhus' orders to the end. I think thats useful
While I think this scene was showing us that Seswatha may be more alive than we were led to believe, I think there is something of vital importance here. Post torture, during the escape, Akka goes what amounts to super-saiyan (and/or Avatar state), briefly becoming more powerful than he ever could have been on his own. If all the Mandati could be triggered into this state during a full scale battle, they'd be even more extreme of a force to be reckoned with.
Maybe Kellhus was counting on this and it didn't happen, he expected them to go into the Seswatha State under the extreme pressure of a devastating surpise attack, for long enough for him to come to their aide, and certainly long enough for most of the Mandate to survive pretty much any onslaught.