@SoggyShorts explained the difference between base and actual production so no need to elaborate on that. So I will only add some thoughts as to if it is good or bad
Many AW work this way, the benefit seems very small, the point is however to consider that you will get the benefit from this point onwards until you either delete the AW or stop playing, so if you play for a couple of year the benefits will be enormous. Best example for this is the Martial Monastery/Sanctuary: It is one of the best AWs in the game, but the hitpoint bonus is tiny (the culture is just a nice extra). But every hitpoint you gain are troops that survive in every fight you do forever. It sometimes only saves a few troops (usually, this is what it does and that is great in itself), but sometimes it will make the difference between winning and loosing a fight. In a high tournament province that can mean hundreds of thousands of troops in one encounter (that is the occasional bonus).
Also there are not many AW that are awesome at level 1. Most need upgrading to say lvl 11 or 16 before they become good. And if an AW is worth upgrading to lvl 16 it is also worth upgrading to lvl 30 (well or at least 26, the last full powered rune circle). Since it will take a while to do that you better choose your AWs wisely (most people don´t of course).
Now as to your Mountain Halls: It used to be a staple of every city (and because of that it still exists everywhere) for a reason. It has two very nice effects: It gives population based on your working pop (which means more and more as you grow your city) and it gives a boost to goods, the only possiblity to permanently increase production once you have reach full relic boost (all other measures are temporary). Both in itself would be reasons to build an AW, but together it makes a great AW. The only problem with it are the new tourneys. The MHalls now make the tourney more expensive without it being able to reduce costs more than that (the goods boost is not THAT big). But out of all the AWs that do not make tourneys better it is still one of the most useful (together with the GA, the other pop AW). I personally am not only a tourney player but also a FA player and MHalls help with the new FA system, so I can add that as a little bonus to its general usefulness and accept the effect it has on tourneys, but it sure is not an AW I would push past lvl 11 or so early on. Much better to focus on the really important AWs nowadays.