I'm considering changing "X-LoadOn-Always: delayed" behavior slightly to make "delayed" mean "not in combat".
This would be a slightly incompatible change, since IF you want something loaded when you log on into combat (think crash/disconnect in a bossfight), you would have to explicitly add a condition to load it during combat.
If there's anyone wildly against this, please say so here or in the ticket.
To everyone else using delayed loading: consider adding "X-LoadOn-Combat: true" already if your addon is important for combat. It's even a good-ish idea without the change.
I'm also wondering if "X-LoadOn-Combat: true" does load the addon before the combat lock up, so they can create any needed secure frames (or whatever cannot be done in combat).
Good question - it "should" since it does all the processing and loading inside the event for PLAYER_REGEN_DISABLED (where we should be able to do noncombat stuff still, according to Blizzard), but I for one haven't actually tested that it works, and I have to admit that it IS somewhat of a special case with going ahead and loading a whole addon inside the event handler.
I'm with Nevvy, it's rare for you to *need* to load properly in combat, so if you do you should be taking extra steps to ensure that works in the first place. Using both delayed and combat triggers will probably cover you, then if you log in mid-combat it loads immediately, otherwise it loads delayed.