Emberquake is a superior ability compared to Flame hammer in Synergies.
SuperCharge can proc from Emberquake if you slam emberquake in the face of an enemy as that for some strange reason counts as a melee hit then.
Forcefield and Aegis is a great combo in Darkness Falls (T1) depending on your items, if you go for items with Parry you can reach up to 160k absorbs when Aegis procs, but for Derinkuyu it is rather "meh" but the Engineer does not have a lot of good abilities, so even for Derinkuyu i would recommend you to pick up both Forcefield and Aegis of Fate.
Physical damage reduction from the passive is of no importance, since you will need to get 75% Damage Reduction anyway (to everything) having for example 50% damage reduction to all the elements and 75% physical would end up with you dead. People pick up that passive mainly for the +%Physical armor and early physical damage reduction which helps a little in the start of the gearing up process, it gives Aegis of Fate higher absorb shields when it procs.
Mines on the Engineer has in my experience been bad damage, the best Engineer Ability is Emberquake, spam it all day long.
I would recommend you to get 15 in Immobalize copter as that works on bosses, and also 15 point in Onslaught, works on bosses as well, so a lot of -attack/cast speed on bosses, which is great, and the Heal bot doesnt just heal you, also gives you a small amount of physical armor, which is giving you bigger aegis of fate shields, tho in Derinkuyu (T0) Aegis of Fate procs wont be all that big, 13-20k shields i think.
Charge Reconstitution and Charge Domination are quite useless Abilites imo, you should drop them and use something else instead, dont forget the Synergies Health/Mana potions, just use them all the time (I have mines being autoused as a macro so i dont have to get cramp in my fingers after several hours of play), also drop Seismic slam and Fire Bash, they dont work on bosses and you do more AoE damage with Emberquake anyway, Seismic slam is good for trash mobs tho.