There are two things to consider in an or block, the logical TRUE/FALSE and the objects it picks (feeded to the actions).
For the the logical TRUE/FALSE, an or block is the same as the conditions seperated with a copy of the actions.
(yes i know its more code). If you are not picking objects, yes plz use an or block. And no, it dont accept an AND middle in the OR.
For the picking, if the or block contains a second condition picking the same object, then its starts from what is previous picked in the first condition picking that object. It will then happen that the logical TRUE/FALSE is correct but that there will be no objects feeded to the actions, due an empty picklist.
If you dont think an or block really trough, you are better of anywayz with a block for each condition and duplicated actions.
My 2 cents.