You missed your trigger, so call me maybe.
Over the past few months, I've had growing concerns about Citadel Siege's beginning of combat targeted trigger. The only reason I didn't write about it in this space was because Citadel Siege was a rare, so showed up rarely in Limited, and wasn't a big enough player in Constructed to warrant writing about.
As it turns out, Citadel Siege is beginning to see some fringe play, and will likely continue to build up steam in Constructed, but it has been completely usurped by Surrak, the Hunt Caller. This guy is the real deal, unlike his alternate timeline self. (Weird how many of the former Khans became better cards in the new timeline.)
Let's say you control a Polukranos, World Eater, a 5-power creature, and cast Surrak, the Hunt Caller. This gives you the 8 power you need for formidable. You turn both of your creatures sideways and say "Attack for 10." Your opponent calls over a judge expressing concern about the Surrak trigger. Is it missed?
Surrak has a targeted trigger, so the rules require you to choose a target before you pass priority next. However, what's going on here is that you're executing a shortcut. As it is illegal for the Surrak to attack the turn you cast it, it seems clear that the shortcut is "move to combat, target Surrak with his own trigger, declare Surrak and Polukranos as attackers, deal 10 to you."
The problem is that's a lot to cram into the shortcut "attack for 10" and the less you say explicitly about what you are doing, the more chances you take that you could be missing something in the sequence, and you are leaving your actions open to interpretation. The trigger rules state that "the controller must announce those choices" not "the controller must heavily imply through their actions."
One case when the rules are clear that the trigger is missed is when a player uses a typical combat shortcut. "I'm ready to go to combat" and "declare attacks?" are two common examples of these. These shortcuts " offers to keep passing priority until an opponent has priority in the beginning of combat step. Opponents are assumed to be acting then unless they specify otherwise." Combined with the missed trigger rules that state that you must announce targets when the ability is put on the stack, the use of this shortcut means that you are passing priority in the beginning of combat step when the trigger should already be on the stack (and thus have a target declared). In order to not miss the trigger here you need to make it a part of your shortcut. "Go to combat. Surrak targeting himself" or some variation of that.
As with all "Is It Missed?" entries, this policy applies at Competitive REL. Let me know if you want me to write about missed trigger philosophy at Regular REL as well.