Edit: I've come to the conclusion the following is irrelevant. See my next post below.
Then, Jorrit, the question becomes: does that attack originate from
you or the sustained
effect?
"The “Sustain” entry tells you if a power has an effect that occurs
when you take the action to sustain it."
- PHBp59.
"Some effects do something, such as an attack, when you sustain them"
- PHBp278.
I had to look hard to find an example that explicitly supports the notion that these sustain attacks do trigger an OA. And I believe I have found (at least) one: "Delusions of Loyalty" (page 138).
Its sustain line say "When you sustain this power, you can repeat the attack against the target."
Here it's clear that
you can make an attack, and it's equally clear that this attack is a ranged one. Thus it triggers OAs.
But there were a lot of powers where I
don't see this support. I'll just take two examples (out of many):
* "Curse of the Black Frost" simply says "The target takes 2d8 cold damage." No attack is even mentioned.
* "Summons of Khirad" doesn't mention you making a (ranged) attack, so no OA. It only says "Make a Constitution vs. Will attack against the target." The rules doesn't explicitly define this attack to be ranged (even though it is a Con vs Will attack just like the main attack of the power, which
is ranged). (Here however I
am open to a possible rules clarification from WotC that say that such undefined attacks do use their main power's ranged/close/melee indicator)
In short, there is no one true answer. But those OAs trigger on a lot less powers than you'd think.
Hope this helps.
