The opener ticked all the Arrow boxes - both good and bad - and I thought it was pretty good. So we had some good stunts like the truck losing it's wheels, melodramatic hero speeches, couple of amusing moments, new baddie (who already has more presence than R'as thanks to Mcdonough), cool new toys, lots of fighting, some good plot twists, flashbacks, crossover and nice cliffhanger.
On the bad side we had Willa Holland not up to stunt fight standards yet (and no gratuitous bellybutton shot!), body armor that is useless against hero bullets (but at least it works on cop bullets this time), Lance still being grumpy Lance and ...
Diggle's helmet. I was wrong, it doesn't look better in motion. It's just too small. Why they designed it so the cheek pieces don't come down to cover the sides of the jaw is pretty dumb. It serves no real purpose being that short on the sides. It looks like it was designed to be worn with body armor with high neck protection so maybe there is an upgrade from that jacket coming.
All signs point to Felicity in the grave but I'm thinking it may be Diggle's wife. She's just familiar enough to be a loss but not integral enough to matter that much. I don't know which is worse, because the fan reaction to the former will be pretty bad but if it's the latter the Diggle/Oliver relationship becomes even more hostile.
Of course there is always a Lazarus Pit around the corner and we know Constantine is making an appearance. That could also be to deal with Darhk and Thea too but you never know who stays dead from now on.
In response to why the security in the meeting was so bad. Darhk is a sorcerer. so security doesn't pose much of an issue when he can seemingly become invisible or teleport.