From the Wiki " The races agreed to give their magic to the seers, who would seal it within a Bloodstone, starving the Dragons. The mursaat, however, having found a way to become invisible, to literally become out of phase with Tyria, betrayed the other races and left them to rot, keeping their own magic and fleeing into a half-world. Some time later, at the time of writing of the Tome of the Rubicon, they warred with the Seers, nearly wiping out the race"
There it is stated that the Betrayal of the Mursaat is not the Genocide of the Seers but the withdrawal of the World. Slipping out of Phase and the Tablet doesn’t even state that the Seers wiped themselves out. They had a Civil War after the Dragons went to slumber again but the outcome has not been stated by the Tablet.
And trying to hide in the War itself and then get hidden by Glint doesn’t contradict each other.
Ok lets make sense out of that.
10.000 Years ago the Elder Dragon’s awoke.
The five Elder Races forged an Alliance to fight them Back, but they couldn’t agree on how to fight them.
The Mursaat and Forgotten went for a more direct Approach and the Seers were working to store Magic, while the Dwarfes and Jotun went for a more defensive approach and tried to hide after, we don’t know, many years.
Then the Mursaat and Forgotten attacked Zhaitan and failed. Mursaat were getting kittened at the other Races and the Forgotten after that went elsewhere. Somewehere after that Glaust was being freed from Kralkatorriks Control, trying for a something different to get an advantage, didn’t worked really since even after freed, she remained loyal to his Master for a while.
The Seers then made a Suggestion. They knew how to store Magic and dveloped the Bloodstone. They suggested that the Magic of Tyria had to be sealed to starve the Dragons, and every Race also had to give in their Magic. The Mursaat, being kittened at the other Races said " screw you" and left the World, not giving in their Magic and withdrawing every Support they gave before that, thus betraying the other Races. Even with the Bloodstone it seems that not all Magic could be contained and the Races had to hide to survive, and this is where Glint comes in, who hid the Races. Something the Mursaat didn’t seem to know,
Ok now the Races were hidden and the Elder Dragons were sleeping again. The whole Cycle left s an impact on the other Races. The once mighty Jotun devolved into bloodthirsty Brutes. The Seers also seem to have a Society Collapse with violent Tribes warring each other for the Control of the Bloodstone. And well if the War between Mursaat and Seers started, it started there. We don’t know if the Seers were still warring then or had a funtioning Society again at this Time. Perhaps we get more information about this.
Well there are still some Holes but integrating the Tablets with the known Lore is possible without retconning the Lore of the Elder Races.