Motori Jan it may be do to my limited knowledge on this subject, but is this ahvaazi seperatist movement as small and insignificant as you say?
Iranians don't like to hear Separation they despise that word and all these separation mongering groups in Iran clearly remember what happened to Kurdistan Democrats and Komeleh groups They didn't loose because Gov. crushed them they lost because no one supported them. If they had the support government wouldn't be able to have a carte blanc eliminating them.
We know the Bush administration has been supporting sunni groups such as Jundallah to try and destabalize the I.R., so why would they not try with these groups in the East? Is it that futile?
You say "We know" but I personally don't know that, quite frankly after 9/11 I don't believe any US administration will support a militant group in ME who has decorated their logo with Allah, may be that is the reason Jundollah changed its name to some thing else (Iranian Liberation something) because they didn't receive the attention they were expecting from US.
There must be Geopolitical, Economical or Military Strategic objective for US to support an opposition group capable of high success rate, any group without internal support is bound to fail and it would be beyond logic to invest in a deal which you are certain it is doomed. Al-Ahvaaz or Jundollah group have no internal support what so ever you don't even see their name being mentioned in Iranian blogs.