In considering the multitude of items in DOTA, there is also the fact there needs to be because the items, in most instances increase a specific attribute, such as STR, DEX, and INT, which gives different bonuses, they can be more useful to specific hero types. With the current version of Demigod, there is no middle layer of attributes and items just directly impact the end results so they become generic in their own right.
If there isn't item drop or a concern about the enemy stealing something, this smaller more generic version of weapons does accomplish the same on the end game strategy. The drawback is it is very bland with the lack of accomplishment to create your personal weapon, you are simply paying gold to get the end stats.
Also, considering at present we cannot see what the opponent is carrying, we cannot use the strategic value inherent to know what they might be from tiered building . In Dota if you saw a hero with specific small pieces, you had an idea what they were building and could work on your own way to counter. Again, it seems like a small thing, but it added more to the play and gave you alternative ways to counter. So I guess it would be cool to have tiered building, but it would have to be more than just combining items to get the full benefit to the game play.