Panny: I guess your mileage may vary. Some shaman have mana issues, others never do. It all depends on your gear, your raid composition, and the encounter.
It's impossible to have a realistic "dps weight" for mp5, int or stamina, because there is no direct connection between them and the other dps stats. At best, you should establish the amount of mana used in a 2 minute burn cycle, and develop a formula to express how much minimum mana a shaman would need, based on his AP (since AP directly feeds your mana regen with SR). mp5 is going to always, always, always be an inferior stat to Int for a decently geared shaman, since that shaman will be regenerating more mana with SR than he has room for in his small mana pool, and Int is a much cheaper itemization stat.
Furthermore, a 'full burn cycle' of mana consumption is nearly always constant, so there's not a lot of variables involved. Just determine the formula needed for complete sustainability based on buffed AP and weapon speed.
Personally, I raid with a Ret pally. <3 JoW
