Listening bit by bit.
Solid advice so far.
I disagree with you on imps though.
Me 5+ is not wonderful, but with 24 attacks and vicious they can put some damage out. The main thing is that 14/16 is pretty good for 105 points. Even with De 3+ they tend to last quite well. Things that can kill them in one turn have better things to do than kill a 105 point unit and other cheap stuff and chaff take a while to get through 14/16.
Also great for objectives that are too far from the action to warrant significant attention.
I used to (sold my daemons when I gave up on warhammer) run two hordes on the flanks of a lower abyssal horde to make a decent but cheap infantry line.