That'll work, though it would probably be better not to have it (temporarily) change your focus, since that will make it unusable with actual focus macros. Just use UnitName("mouseover") to get the name of your current mouseover unit.
Code:
/use [@mouseover,help,dead] Raise Ally
/stopmacro [@mouseover,nohelp][@mouseover,nodead]
/run local c=IsInGroup(2)and "INSTANCE_CHAT" or IsInRaid()and "RAID" or IsInGroup()and "PARTY" if c then SendChatMessage("Brezzing "..UnitName("mouseover"),c)end
I also added checks so it won't try to cast on hostile targets, and won't send a message if your mouseover target is hostile or not dead.