What are the odds?

I can't really tell you the odds, but if you're only after a single DC, then I would say go ahead and pull at this legendary banner.
400 orbs should be enough to get one Hector if you're sniping for green orbs.
Got 2 red 5 stars with only about 30-40 orbs spent.

It will takea while till they release a "Hector banner" considering that the last one was lika a month ago, maybe two.

I would recommend doing 1 or 2 full circles first just to get that pity rate up before sniping (If you get a pity breaker you spent a max of 40 orbs for it - which is actually a pretty darn good return).

Based on improved calculations I devised yesterday (thanks to SourPeridot for spurring me to it), the probability of finding LA Hector at least once pulling only greens except when there aren't any (the calculation now accounts for this phenomenon, which is frequent when trying to go for greens only) is slightly below 90%. So it's possible to fail with 400 orbs, but you would succeed 9 times in 10. Oh, and my calculations assume no pity rate because calculating with pity rate requires better skill than I have, so it's 90%ish even if you get pitybroken along the way.

If you don't like the other greens, though, you're getting a pretty poor offer for your orbs. If you're that desperate maybe you don't have a choice, but it would be ideal if Hector appeared on another banner or the next legendary banner (L.Hector returns if I'm not mistaken) has good greens.

I spent like 460 Orbs when L!Hector first came out, and guess what, i only managed to pull 2 Myrrh's with all my orbs, the rest were "pity breakers" from other colors.

Just pull with caution, because the worst possible scenario can hapen.