The thing with Moser's is is gives you good blocking % (but not the absolute best), blocking speed, and resists (but not the absolute best) AND those sockets, so it's up to you do decide what to augment with those sockets. Diamonds are the most popular as a one-item solution to the Hell resists penalty, and it's a dirt cheap option, so you can't really go wrong with that option as long as you have a Hel rune sitting around to clean the sockets out if you have another idea.
I would put 2 pDiamonds in it and go since it's useful like that to a wide variety of characters like that - also, Moser's isn't that rare, and if you want to make something like a FishyZon (Bow/Jav hybrid - so you don't want to be relying on the shield for resists because you won't have that on your bow switch), Moser's is actually beat by the SET round shield, Whistan's Guard - no resists, but the best blocking in the game by far.
RobbyD, I do basically play all 7 characters over the years, depending on my mood, with a bowazon, a fire elementalist and a cold sorc being favored. I have a pally and a barb, both in the 40s, still with no specialization, just battling on. A necro and an assassine in the 30s, with still a lot of points to distribute. I have Whistan's, too.
Well, having a Moser's with 2 pDiamonds in your stash is not going to be a waste, especially for as many characters you are developing. It's kind of like the "Honor" Knout I made for my Barb before I developed some knowledge and wealth - even if it doesn't ever see whole game use, it's certainly handy in enough situations that having it available will be a good thing (my MeteOrb sorc is using that Knout from level 27 to 30 where she will transform to a skill-only killer - I don't know of a better melee weapon for that level range).
But the Moser's with pDiamonds is good enough for long term use - I think the Sorc or pure JavaZon might benefit most from that shield - a pally and a necro have better character specific items (HoZ and Hommy), a Barb and Sin will likely dual wield, and a wereform Druid will likely use a 2H weapon, but a Sorc can make great use of the Moser's probably throughout the game - you might consider upgrading that at some point to increase the blocking since the Luna has better base blocking than the Round Shield (only once you are rune rich, though).