The round spent casting True Strike is going to seriously reduce the damage the spell gives. You're just making the spell worse. Witch Bolt isn't a good choice up to level 4, at level 5 it's worse than cantrips. Even if you stick it in a 9th level slot and do 9d12/round with it, it's still pretty much meh unless maybe you twinspell it or something. It was really dumb of them to make it take up your concentration, I can't see it getting any use for non-sorcs.
I don't see it that way at low level.
At low level, 1st and higher level spells are at a premium. So, I do not want to waste an entire spell rolling a crappy to hit (which happens a lot for me) and missing.
I'd much rather cast Twin Strike round one and Witch Bolt round two and have a fairly decent shot of hitting than cast Fire Bolt rounds one and two, hitting on one of them, and averaging less damage. In the Witch Bolt case, I've also set up round 3 to autohit.
Sure, things can happen to disrupt my plan, but I'd much rather contribute to the party by casting one non-cantrip spell than contribute to the party by casting one non-cantrip spell plus a boatload of cantrips that for some reason, seem to miss an awful lot.
Note: Also, I did not learn Fire Bolt. I learned True Strike, Chill Touch (anti-undead), and Acid Splash (multi-target). So for my PC, Wizard Bolt is even more powerful than a cantrip.
And Witch Bolt basically limits an enemy spell caster from casting concentration spells. He can do it, but he'll be making a concentration check every round. At higher level, it's not about just damaging a foe, it's also about disrupting a foe. A simple first level spell can disrupt a portion of an enemy spellcaster's repertoire at level 10 without the wizard or sorcerer using up a lot of resources. Granted, an enemy spellcaster might know to move away (recognizing the spell), but again, the time to do it is when that spellcaster is engaged, that way, he either disengages or provokes.