You may very well find a guild that doesn't have attendance requirements, but just about any guild that is capable of getting epics for their members and encountering Velious raid mobs is going to have a minimum attendance if you want to bid on dragon loot. This is the norm in most (all?) raid guilds as I'm sure you can understand the negative side of showing up for a single dragon and spending latent DKP earned months or years ago on a high value item to win over a member with 60% attendance that is currently very active. Current active members take an even higher priority on loot council guilds for obvious reasons.
I'm less familiar with main/alt declaration in other guilds but it is also something that exists to protect that hard working main from being outbid by so and so's alt. Even though it sounds like your intentions of playing all of your toons equally is pure, it still probably won't happen.
TL;DR The competition level of end game raiding on this server is so high that unfortunately low/no attendance will likely get you little to no loots.
Legday <Asgard>