I’m playing quite casually so please forgive my lack of knowledge.
I know that when a Legendary item gets an affix update I have to find it anew in order to obtain the effect.
( I still have a primal Squirts with no affixes for some time )
So my question is, does this apply for class sets as well? Would be a shame because I have the Manajuma set for WD (both items in primal)… twice.
Hello,
The short answer is No; changes to the bonus(es) granted by sets are retro-active and you will not need to find another one to benefit from the new bonus(es).

For example, in the current PTR, the damage from the angry chicken explosion is being increased from 400% to 2000%. If this modification makes it to the live version of the game, all your Manajuma’s set items will automatically have that improvement.
There is a special case… some set items also have their own powers… such as the Krelm’s Buff set… the belt and bracers have their own powers – the belt increases run speed by 25%. If, for example, Blizzard decided to increase that number to 30%, then you would have to find a new belt to get the 30% bonus.

Finally, note that if an item power is being reduced, then all the existing items will have the new, reduced, power.
I hope this helps.
Much thanks for the response!
Everything is clear now.