Slayer is quite good career now, but his ‘Dawi-drop’ is not worth to take.
Yes, someone will say you can one-shot CW with this talent even on Cataclysm difficulty, but if you want to use this talent properly, you should charge into CW whom is with horde, very unwise thing to do.
And you must giving up ‘No Escape’ which gives you extreme survival ability.
I think Dawi-drop can be more interesting choice, if it gives massive damage to first attack while you are on air, or first attack within 1 sec when you landed on earth. (‘Big-shot’ like Bounty-hunter, Shade, Grail knight) So you can play slayer as Monster slayer as lore-said.
but Slayer is already extremely good for horde, and killing elites. It’s unfair to take these all the good things, So If you choose Dawi-drop to be a Monster-slayer, It gives some penalty to cool-time (since you can restore your ult really fast with talent), and loose attack-speed when you are on ult.