crits dont double damage, they only add 50%, so its 75 potency just from that.
after that, you have to realize dragon kick can crit to, so its not a full 75 potency increase, its closer to 65 (its actually less but just for you i'll round up)
now then, its only going to make a difference once every 7 skills, we per skill we get an average potency increase of 9.29
to give you a reasonable sense of just how small that potency is, i'll tell you my dragon kicks average at around 1000 damage without crits (i185)
the damage boost from swapping a dragon kick out for bootshine will take place once every 15 seconds if you have no skill speed
the boost in damage is 400 damage assuming a 20% crit rate
400 divide by our time (15) comes out to be 27 dps
27 whole dps.. wow... yeah thats some game breaking damage there.
now then, if you want to prove me wrong or say everyone thinks a second monk really is just 27 dps, then go right ahead.
edit: corrected to once every 7 skills
