I searched various forums but couldn't find anything specific. We read a passage along the lines of assigned damage tokens can't be blocked but the language on the cards always talks about dealing damage and assigning dice so... Can damage dealt by tactics cards in combat be blocked or do you automatically put damage tokens out?

Yes. The part about damage tokens just means once damage makes it through, in a later round you can't retroactively block it.

To clarify, both dice and tactics cards deal damage and after you designate the targets, the defender's tactics cards can prevent damage from occurring to the designated units, whatever the source. Damage from dice and damage from cards follow the same rules.

But at the end of the battle phase (after the defender has had a chance to block damage), all unblocked damage from cards and dice is converted to damage tokens (unless the unit was destroyed).

The part about assigned damage not being blocked refers to these tokens. In essence it's saying that if your corellian corvette takes 1 damage in round 1 (and receives a damage token) and then takes another hit in round 2, playing a tactics card to prevent 2 damage would not let you remove the damage it already sustained. That damage token once acquired, cannot be removed by any means before the end of combat.

Whether it came as the result of dice or cards does not matter