There isn't a stat which is more important than another imo. You need a good balance between the 3 stats. Your build and gear also depends on boss you Are tanking. Against bosses with high auto attacks you need decent hp and high armour and def, against casters higher hp can be more usefull than def and armour since the most dmg comes from skills. My suggestion is, since the majority of bosses deals the most dmg from high auto attacks, high defence works very well. I run around 6.7-6.8k defence lixless and i have no probs, especially against auto/physical dmg based bosses like 210 edl is perfect (i managed to tank 210 edl 6* with just one ranger healing me using an high def armour based gear). It's just a matter of experience, keep practising and tanking all different kind of bosses and you will find the tanking style that suits you the most. Gl, hope i helped you out
