personally i know 3 techer, te/hu, te/fi, te/ra
te/hu = this is one my class and i love it, because its basically fighter/hunter minus the gimmick, this is the class if you like simple things, there are no strange gimmick like other class (weak bullet, guard charge, adrenaline, etc) just pop shifta and deband and whack them all, mobs? just pop zondeel and look at that fireworks when you hit them. they can deal respectable damage, not amazing but not bad either. this class is pure melee, you can cast tec but you do far better with melee, your tec mostly for utility and buff (resta, ilzonde, zanverse, etc)
te/fi = this is the all rounder techer, they can hit and their tec damage is also ok, because of that their damage is so so compare to te/hu, they can however start hitting hard if their chaser damage skill is active (more damage if enemy got status ailment) and since your sub is fighter, you deal even more damage if your hp drop below 25%, its basically do or die techer, above 25% hp you doing average, below 25% is where the shit start happen, its very risky but if you want to go te/ph later in the future, te/fi is the best techer class to get used too because te/ph playstyle is almost identical.
te/ra = is pure support class, you do the least damage but your support is the best without any doubt. on the techer side you got the usual resta, shifta, deband, zanverse, zondeel, etc. on the ranger side you have your stun nade and weak bullet, the weak bullet alone is huge help for your party because of the extra 20% damage boost. its probably the least played class combo, but if you want pure support, this without doubt (for techer main) is one of the best support