I gotta agree with this post.At top level when every little dps counts, and when progress is measured in weeks sure.And even then, guilds are doing splits to ensure healers are well geared from heroic, this isn't dota where you are progressing the last mythic boss with your healers having brown boots.
When you're past world 50, honestly that dogma applies negatively to guilds progressing, where you should keep on eye on who is likely to stay in the guild/be an asset and not on the OP example above.