Am I obligated to give [Phaseshifter's Bracers] on ms roll to resto shaman when he roll top, but i had resto druid which rolling for the item.
Or i must stick with that , that he can take mail bracer (as his mastery) and give it to the druid.
I mean - i gave it to the druid, but im concern now, cose there is interpretations of the rules
Both classes have equal use of bracers. Otherwise it would result in banning every non-cloth caster for rolling on BiS cloth items (due to leather/mail/plate analogies being worse)
Resto Shaman can make use of the item, and rolled highest, so it should've been given to him, kinda..
There's no benefit as healer or dps to have the matching "highest" armor type of their class. What matters are the stats on them. Shamans CAN wear mail, but nowhere in WoW reads that they SHOULD (at least up to WotLK). At the same time, people are somewhat expected to respect the clothes for cloth classes, leathers for leather classes etc. Works better during gearing from 1 to 80. Raids, not so much.
The druid and the shaman would've rolled for http://wotlk.cavernoftime.com/item=54582 if those would have dropped, and you guessed it, cloth classes would get mad at druids, shamans and possible holy paladins rolling for it, because those classes could roll for leather, mail and plate, while themselves can only roll cloth.
Ninja rules in raid environment are always up to interpretation. In this case, it's up for debate if you did right or wrong.