I was in the same situation. I joined a guild and had some expectations of how it would play out. As Im a very hardcore and progressive minded person, I got abit annoyed by the structure they decided to go with. A 25 man guild who raid 3 days a week. Having 38 people in the roster, some beeing bad players (imo). Swapping people out and in all the time when a new boss is inc just for the sake of letting everyone play (even tho it hurts the progression as bad players are in, but as well as "wasting" loot on those players, as they have "same" chance to get items due to epgp). Tho the loot council decided weapz and tier pieces. Which was't distributed with progression in mind either. I made a huge thread on the forum explaining the current flaws I saw with their structure and asked what the guild's "goal" would be, as well as talking to the GM who said things would change. But when I noticed that they had their mind set into another direction than what I would pref, as well as deleting my whole thread which (honestly) pissed me off quite a bit, I took my leave. I wanted a small roster with a core beeing in focus rather than thinking all 38 people should be considered the core.
Their attitude was kinda like this :
"It's been working for us since ever, people tend to randomly leave and it's good to have backup." From where I was standing, it looked to me that alot of good players left due to just that reason of beeing benched to let the lesser skilled get some raid time.
From my experience, if something annoyes you, your only option is to bring it up and hope for something to change, or simply take your leave. Because playing with things around you, that pisses you off, will usually put you in a bad mood. And I for one don't have fun raiding when Im in a shitty mood. I trial period is not only for the guild to see if you a worthy a spot in the raiding team, it's also for you to see if the guild will fit you and if you feel you belong there or not. So I would suggest you bring it up with the GM and the officers, rather than just sitting there waiting for a change that might not happen.