yeah two weapon fighting is broke right now.
off hand shouldn't get the extra damage, thats the whole point to the fighting style
off hand bonus action attack should only be an option after making a standard action attack
rogues shouldn't be getting two bonus actions, as it creates way too many balance issues.
is it part of 5e that offhand attacks cannot be taken first?
I have to address this first: In 5e there is no "offhand" attack. You can decide what weapon you want to attack with with your main action, and your bonus action is to attack will be with the other weapon. You can basically consider your character to be ambidextrous as it doesn't matter if you attack with your main or off hand, all that matters is what weapon you attacked with first.
With that out of the way, yes, in order to make a bonus action attack because you are wielding two weapons, your Action must have been to perform an attack:
Two-Weapon Fighting
When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand. You don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
If either weapon has the thrown property, you can throw the weapon, instead of making a melee attack with it.
