Is there an official answer to this very important (yes, I'm playing a wizard...) question ?
Not quite sure where you're getting this from:The OA comes from using a power; it's the Use a Power action that provokes.
PHB said:Opportunity attacks are triggered by an enemy leaving a square adjacent to you or by an adjacent enemy making a ranged attack or an area attack.
That's the way i play it.My ruling is that sustain should not provoke regardless of what action it takes to sustain or what sustaining does. Only the initial activation of a ranged or area attack power should provoke OAs. Thats how we play it in all the games I play in and it has not been an issue.
PHB said:Opportunity attacks are triggered by an enemy leaving a square adjacent to you or by an adjacent enemy making a ranged attack or an area attack.
Summons of Khirad said:Daily <snipped non-relevant text>
Standard Action Ranged 10
Target: One creature
Attack: Constitution vs. Will
Hit: <snipped non-relevant text>
Sustain Minor: Make a Constitution vs. Will attack against the target. On a hit <snipped non-relevant text> the effect ends.
So....
1. Wizard cast Freezing cloud
2. There are creatures in Freezing Cloud
3. Some creatures move to surrond Wizard
4. It's the start of the creatures turn in the Freezing Cloud
5. Wizard rolls to hit creatures in cloud.
6. Creatures around wizard get to make Opprotunity Attacks on Wizard
...
"Sustain minor" and does not say "Sustain minor range 10."
PHB page 290 said:When you are adjacent to an enemy, the enemy can't ... use an area power...wihtout ... allowing you to take an opportunity attack...
My ruling is that sustain should not provoke regardless of what action it takes to sustain or what sustaining does. Only the initial activation of a ranged or area attack power should provoke OAs. Thats how we play it in all the games I play in and it has not been an issue.