Backflags for events, yes, but not the faction requirements. Adding a faction hit equivalent to a completion of "Shade's Bounty" (collect 4 Mark of Rallos Zek) to each raid event, and about half that to "Large Events" (the ones with aug loot) would have a lagging member's faction capped out in about 4 full clears of FC1 & FC2 with a raid, I think. My guesstimate is based on my feeling of magnitude on Shade's Bounty, which was a very significantly smaller hit than doing the major progression missions of Shade's Bane and Incursion.
Actually backflagging lower playtime members and apps is nearly automatic; we're caught up already and any new people pick up the flags immediately. The persistent issue for raiding guilds are the associated factions. "Scholars of Solusek", "Infiltratiors and Traitors of Ashengate", and "Wraithguard Leadership" factions. Those who put in the time raiding to be part of a group that CONQUERS THE SERPENT"S SPINE recieve no faction for doing so. Faction is wholly based on the considerable time spent on tasks outside of raids.
To be clear, I'm quite firmly of the opinion that factioning via a raid should be the long & hard road compared to doing it right through tasks & missions, but the alternate road needs to exist so that players aren't in the situation of being gimped along with thier buddies after having personally beaten the most strenuous challenges the expansion has to offer.
Tangentially: in the future, flagging systems that flat-out exclude those that aren't flagged ... in a twisted manner... cause less drama in the end. The "key yourself of pack sand, slacker"-ultimatum is motivating and concrete The way TSS "kinda" requires this and "sorta" requires that, but "if your friends maybe.." something else... makes life hard for those the developers should care about helping most, those that put themselves out to navigate the system. Any drama needs to be out of those peoples' hands totally, if it can be arranged.