This is one of those really difficult things. I agree that there shouldn't be any recruiting for other guilds in a guild's official forum, regardless of how said guild is doing. The only time I can see it being ok is if/when the guild is shut down entirely as an option for the people being stranded. It's just straight disrespectful for the people currently active in the guild. Do unto others and all that.
That said, Redeemed is in a catch-22 state right now. It needs more active members in order to get more members. I had stuck with Redeemed so long after its glory days that I forgot what being in a large and active guild felt like. Then I met my now wife and moved a character over to horde-WrA to join her RP guild... and it was a completely different game, logging in at off hours and having 10-15 people on, and actually seeing other guildies randomly while doing stuff in the world. It was a literal breath of fresh air into my WoW experience (I was slowly growing more and more bored with the game, because the social aspect just wasn't there). Ever since I've spent less and less time on Redeemed because it just can't compete socially. I feel that this is EXACTLY why people have been moving. Its small size + being on a lowish pop PvP server make it almost impossible to grow back without actual dedication to do so by those who had left it. People play with their friends on MMOs, and for long time players (like me) that usually means server hopping over the course of a career. I've seriously created a mage as my first character on Crushridge, migrated to Korgath, migrated Dunemaul, and finally Stonemaul, and will probably eventually join my characters on WrA-Horde. It's the unfortunate side-effect of sharded servers.
What this means for Redeemed is that if it wants to grow again as a guild, it will have to have an active Guild Leader and a powerful recruitment drive (probably a dedicated Recruiter), drawing back old and incorporating new members. Which will be hard. WoW is an old, old, entrenched MMO with not much in the way of new blood anymore.