First off, I think Volendrung is one of the worst mechanics I've ever seen introduced into a PvP scheme. It creates more clustered zergs when the thing Cyrodiil really needed was mechanics that spread players out more. It's an OP 'insta win' button, a mechanic which really has no place in PvP in the first place. If it it randomly spawns in the current population leading faction (during off-prime), it pretty much kills PvP altogether for the following 30 minutes as the smaller factions can't compete at all and start logging due to loss of morale.
Unfortunately, despite many missteps, it is likely here to stay. So what can we do to make it better? And I don't mean more OP... it's OP enough, just better.
1. Volendrung only spawns for the current lowest map population AND lowest current map point total (much achieve both conditions).
2. It spawns in the most forward current keep of the losing faction and for 10 minutes can not be picked up by another faction (anywhere); after the 10 mins it reverts to current rules.
My hope is that this would lead to some balancing out of low pops vs. high pops during off-prime and give better overall competition during those times. Might even help scores stay more competitive day to day as the losing factions would be able to gain a little ground or hold off getting smashed for a little while. You could suspend these new rules if all 3 factions are pop-locked, but, really, during triple pop-lock the hammer never gets very far, and the damage it does is quickly reclaimed, so am less concerned about which faction gets it during that time (maybe go to the overall campaign points loser during triple pop-lock?).
What Cyrodiil really needs are mechanics that help balance population issues and spread out the fighting across the map - not do the opposite. These are just my suggestions, they aren't perfect in solving those issues, but hopefully it's a start to the discussion.