hydraxian waterlords are not much of a speedbump.
you can start grinding them at level 55, using a group of 4 grinding them if you grind honored in 10 hours assuming 3 kills per min which is quite slow for a group of 4. If that group happens to be humans its even quicker…
Then you have 4 players who can get the quintessence. All you need then is 1 lvl 20 warlock sitting next to the duke along with 2 other alts of any level and you have a summon ready for the 4 of them after the first 4 seals are done and then they get summoned back and all 7 seals are cleared.