MS changes before Halion should be illegal !

Every single time I join an RS25 pug, everything goes fine until we reach Halion. Then suddenly people start changing their main specs, literally mid-raid. This goes against the Terms of Service since loot rules are being changed after the raid has already started.

I join as a Discipline Priest specifically to try and get the GTS, and by the time we've killed the mini-bosses, I’m already saved. Then, right before the final boss, multiple players suddenly change their MS to GTS, adding 3-5 more competitors.

This should have consequences! Changing main specs mid raid, especially before the final boss, is unfair and leaves players like me locked to the instance for no reason.

What consequences do you expect by posting this on the Forum instead of making a proper report?