Bonuses are horrible antipattern. A faction controlling scrolls (or throne) is apparently doing well. Giving it some bonus, so it could do even better, makes no sense. It should not accrue downright penalties for winnig, but accomplishing each subsequent objective should be harder, or at least not easier, which is often not the case in Cyro.

However, as far as playing the map goes, players have two sets of objectives: throning/dethroning an emp and capturing/recovering scrolls, neither of which drive action as well as they could in many typical scenarios, i.e. compel players to accrete in usual zerging corridors to achieve these objectives, rather than to spread out to pursue them.
Consider this: if each faction owns their own keeps and scrolls, scrolls are for the time being virtually out of the game and options e.g. for DC are down to attacking Chalman, attacking Nikel and much less interesting attacking Brindle (= longer ride + PvD at best, longer ride + wipe at worst, depending on whether somebody is scouting). But if elves have, say, EP scroll in Fare, value of Brindle, Carmala and Vlastarus ramps up, because now they relate to objectives.
Another scenario: one faction owns most or all scrolls and perhaps has an emp too. That factions has no longer reason to launch any attacks whatsoever, or more precisely, as long as other factions are not dead and keep attacking, it is far more appealling for it to just sit at its keeps, because it has more to lose than gain by attacking (largely due to the fact that while in field, players can not fast travel (unless they recall/blood port) and therefore attacking to a degree has an opportunity cost) and can comfortably fast travel to battles, which moreover take place around its respawn points. This is not a problem if remaining factions have good numbers relative to the winning faction, but chances are they do not and the current situation is actually the result of it. Then even though there are 6 scrolls, 2 are totally unreachable, 2 can not be picked up and 2 that can be picked up are farthest (and a collision with the other smaller faction, to the benefit of the winning one, is probable, because the other smalles faction has to travel through the same area on their way to their scrolls) and thus kinda can not be picked up either. So there may develop this antipattern situation where things are increasingly easier for the winning faction, because of map design, fast travel, defensive play etc., and very frustrating for other factions due to lack of options, but eventually bad for everyone, because after a string of wipes, smaller factions will turn against each other regardless of objectives to at least have some decent PvP before the larger faction will roll over undefended keeps out of sheer boredom, push them to the gates and everyone will log off, because at this point the campaign will be insufferable.
Obviously it is good if scrolls can be threatened, i.e. are reachable and can be picked up. That provides players with objectives, spreads them out and even more if they succeed in taking a scroll and are on the run with it.
1) At the very least, gates should be always opened and all scrolls pickable at all times.
2) Even better, roll back capturable towns, move outposts between base camps and edge keeps and then move scrolls temples to the sides of Glade/Arrius/Faregyl (and again make scrolls pickable).