To further up on this, if you use Landsouls spreadsheet (Which you should) it gives you extremely detailed guildlines for slamming - for example, mine are:
The GCD will be up at 7.0, WW is still 1 second away from it's CD finishing. So 'wait' to use your GCD for 1 second until WW becomes available.
Basically, don't SLAM! at 7 seconds, because this would push WW back to 8.5 instead of 8 waiting for the GCD to free up.
1 - Don't use new slam passed 1.62 seconds remaining on the 1st Bloodthirst
2 - Don't use new 4pt10 slam procs 1.12 seconds remaining on the 1st Bloodthirst
3 - Use slam after WW ONLY if slam has less than 2.62 seconds left
4 - If the slam has more than 2.62 seconds left, use it after the 2nd Bloodthirst
For ArP and Exp:
Banner of Victory is much better than NES - you never want to use an arp proccing trinket (unless you someone still have... let's say a green trinket). Mjolnir Runestone and Grim Toll have higher uptimes and may be worth it - but the passive ArP is still much better to have. I used Banner until... I got DBW to upgrade it.
Expertise you want as close to 26 as possible - I know that when gearing up it may be a little skewed depending on what gear you can have (Landsouls helps with this so you can min/max your gear in advance and know what upgrades to look out for). If you are at 24 expertise... don't really worry about it too much, unless you really feel like putting that gem in there. I was waiting on a piece of gear to swap out a few for a while and only had 4.7% hit and 24 exp and still pulled number near to my normal ones.