I actually really like the named items as prizes (in addition to the big three). To acquire these items in a different way, you'ld need to get really lucky with chests, or hunt for market deals for ages. To have "just" regular buffs etc as prizes would take away a lot of the appeal of the tombola I think.
Winning an item you already have, or an item that's not that useful to you, is obviously a bit of a downer, but you can always try trading it for something that appeals to you more...
That said, it might be a nice idea to have a "named item voucher" as an extra "rare" prize (similar to the big three) that you could redeem for any named item (but not the big three, tombola items, ...).
It would be a desirable prize for almost everyone (except those that already have everything, but they're hard to please
)
If it seems too good, perhaps have one such voucher per item slot? That would give you enough different options to be able to have some in every draw. Perhaps even always use them (or the big three) as the first prize in each category? You can then "shift" the other options down a place and simply drop the least desirable items from the prize list (the few people who really want them can always hope to win a voucher and use it for such an item that would be considered undesirable by others).