Elemental Shaman are going to be GCD capped, and mastery capped very quickly in 5.4. My PTR shaman has my 5.3 raid gear along with the normal 5/5 new 5.4 tier set and 2 new trinkets (amp and cleave).
With just the normal mode trinkets, the normal mode 5/5 set, and my old raid gear i am sitting at 99.09% mastery, while remaining hit capped, and enough haste to keep my Chain Lightning at a 1.1 second cast, and Lava Burst / Lightning Bolt / EB all sitting at 1.45 second casts. These are 1.1 second casts while under the effects of meta or bloodlust and well under GCD with both up.
So, what exactly are we suppose to do? They didnt allow us to scale with crit, so stacking crit has very minimum gains. We can stack INT again, but we will still be GCD capped and mastery capped even stacking INT. If there are any bosses similar to Primo, we will literally gain 0 dps from the buffs. We currently gain ZERO dps for cleaving / aoe under the effects of Lust or Meta, infact we are probably going to be losing damage on cleave heavy fights by not using the old non legendary meta.
This also has the horrible side effect of making Elemental Blast a 100% unusable talent. A big part of EBs appeal is its +haste/mastery/crit but when you are capped on 2/3 of these things and the 3rd is a very slight increase or no increase at all (get crit buff right before ascendance), its simply going to be a dead talent.
Its definitely fun running around on PTR with all my spells casting doubles of themselves at a 100% rate, but there are too many negatives that come with this. Its just very upsetting to know we will soon see 0 damage increases during lust / meta procs, while every other caster will continue to gain dps and dont deal with being severely GCD capped. With all procs, my chain lighting on PTR is at a .650 cast time... and thats WITH being 100% mastery capped and not having the extra 6-7k or more haste we will have with full 5.4 gear.
Not really sure how this can be fixed. Maybe give elemental a .5 GCD cap instead of 1.0? I cant see them increasing base cast time of all our spells again. We really need crit scaling before 6.0