i wouldnt say the build you linked is terribly defensive, the low HP and no stun immunity means that if you get surrounded, you die from stuns. If you get hit by a decent hit and take an ignite, you wont have that ES for awhile.
It takes a certain playstyle to dip and dodge and not get hit with a build like this, and for these sort of builds overkill damage is also pretty important, which you don't really have (for whatever reasons, i just remember it was pretty low), this damage is also important for freezes on rares and possibly some map bosses. You also dont have the blind, which is really good vs melee bosses and general mapping, cinderswallow is also really OP while mapping for sustain...all this in combination with your low eHP is why you are struggling.
11k ehp and lots of damage is enough to tank a big hit or two and retaliate with great damage, its not a bad build, but it can be made to be tankier w/ more damage, it seems very tailored for a SSF character....if it wasnt for the pledge of hands i'd say its ok...but in a trade league you can for sure make a better character. I would say everything in the build you linked is fine and i would change some items and the tree around, i'd value the ailment immunity and free arcane surge over area and 1k ES and get some glancing blows going to make enemies less of a treat, bosses especially with spell block you'd be able to cap easily.
For you right now, the first thing I'd do is respec sanctuary of thought for end/power charge gen from the other node...this is what really helps your CWDT setup (which i would turn into a non-cwdt setup personally (add enhance support), it is instant). Immortal Call is a great skill and Heiro with this node, and the node is the best way to generate end charges to maintain IC as you dont need to get hit or wait a few secs. You could just maintain IC no matter what, this is incredibly strong and a backbone of defense for the build imo.