Note: if you mess up the Soul Capacitor aspect if you do not kill all of the Quillen that are part of the trash they will respawn when reset. Also sometimes the Quillen will evade on Vanish and other times they won't so a safer way to ensure that your Soul Capacitor hits only Ro'shak is to vanish and Shadowstep followed by using a cancelaura macro for Spirit Shift (Soul Capacitor's proc).
There aren't very many changes on this boss on the Heroic difficulty that are going to be dangerous to deal with however, the physical damage over time effect (Impale) that Iron Qon will continuously stack can become very dangerous once stacked high. Besides Impale this is quite an easy boss fight.
One major change on Heroic is that the Quillen now flee at 25%.
Iron Qon himself does not do very much, but each of his Quillen have mechanics that can be dangerous if not anticipated.
The three Quillen are Ro'shak (Fire), Quet'zal (Lightning) and Dam'ren (Ice).
Ro'shak is of the three the most dangerous as a majority of his abilities are damage amplifying effects which can become dangerous if fought for too long.
Quet'zal does very little damage of note, but if your are left in his phase for too longhe will use Wind storm which means you will have to deal with Rushing Winds. This isn't necessarily a bad thing but as a rule of thumb the longer it takes to get to the final phase the harder it will become to heal through Impale.
Dam'ren also does not do very much damage and part of the reason has to do with his Dead Zone ability. Dead zone cover's 2 sides of Dam'ren's hitbox either the back and front leaving his sides open, his right/left flank and back leaving his front and opposite flank open, or both of his sides leaving his front and back open.
The biggest thing to worry about while on Dam'ren is Iron Qon's Freeze Spear cast which will leave multiple lines of frost on the ground. If stepped on it will leave a debuff on the player that reduces both movement speed and attack speed by 25% for 20 seconds and this effect does stack.
Starting the fight:
I decided to make use of Soul Capacitor here because the longer we have to deal with the mounted phases the more potential that we die to the Impale DoT. Additionally Ro'shak has the most HP of the three Quillen so this makes for a good time save.
Dealing with the Quillen isn't very difficult and if you made use of Soul Capacitor you have plenty of time. Remember that once a Quillen reaches 25% HP it will flee and you will deal with the next one in the order (Ro'shak - Quet'zal - Dam'ren). For each Quillen phase one of the other Quillen will be assisting the boss.
For Ro'shak, Quet'zal will assist the boss, for Quet'zal, Dam'ren will assist the boss and for Dam'ren, Ro'shak will assist.
Once you have brought each Quillen to 25% HP you will now fight Iron Qon himself. When the Quillen land simply pop DPS cooldowns and cleave everything down. Remember to avoid any Frozen Spear's on the ground as getting the Frozen Blood debuff will severly hinder your damage.