You know that using your trinkets and using your adrenals = more time cause of the cool down? which means 1 sec for trink and 1 sec for adrenal means 4.5 second cast total.
not to mention you have to be lucky as hell for both moves to crit. What you're referring to if pretty unrealistic considering it's based alot on luck lol I mean maybe it could happen but chances are slim and you have to use adrenal and trinket.
What the hell is a trinket?
The RELIC and adrenal don't proc the gcd, so you can literally run your fingers across f1-f2-f3-f4 like i do, which takes less than a second, and then cast cain lightning/deathfield. Or thundering blast/chain lightning, or thundering blast / shock, or crushing darkness/affliction. RELICS and Adrenals do not use the gcd.