There are several things you can do to improve WoW performance such as lower view distance and shadows in particular, don't run anything tasking in the background, change from a 4 core to a 6-8 core (from personal experience a FX-8350 4.5ghz has smoother gameplay then a FX-4300 5ghz because WoW uses up to 8 cores). There were also several edits in the World of Warcraft\WTF\Config.wtf that i think that the new Warlords/Legion engine already does by itself now.
SET ProcessAffinityMask "255" - 4 core is "15" -
http://wowwiki.wikia.com/wiki/CVar_processAffinityMask
SET GxTextureCacheSize "11264" - graphics card memory size (adjust for what you have, 1gb = 1024)
SET M2Faster "3" - improves performance in high population servers
SET TimingMethod "2" - starts WoW with a higher priority
Specifically to loading times the biggest impact you will see is change from HDD to SSD like Alaric said, but getting more memory also helps, 16gb should be optimal. One particular tweak i only started using this expansion is to disable "browser hardware acceleration" on the battle.net app, which for some reason helps shaving 5s-20s depending on your system (only seems to work with weak graphics cards, anything less then a 1060 for example).
EDIT: also check if all your addons are up to date and if you have too many they might conflict with one another.