Is it better to:
A) Get off type damage resistance. For instance, vog cub coat with piercing.
B) Get on type damage resistance. For instance, vog cub coat with elemental defense.
C) Align status resistances to provide cover for specific instances. For instance, any fire uv on a vog coat for C42.
D) Attempt to cover weakness; For instance, fire med/higher+shock med/higher on a chaos cloak
E) In a neutral status area like Royal Jelly Palace- use weapons such as gran faust whilst blocking their side effects. (VS boost things)
F) Boost overall stats, or boost a specific area? Is a jelly helm with piercing low+normal low more valuable than one with piercing med, provided that I will not be rolling additional UVs?
G) On shields, is it better to boost them based on their health (a shield with high health would theoretically benefit more from an off-UV than one without) or is it better to boost them towards what they are already good at?
Currently, I've been discovering that option C is extremely helpful provided that there is a danger in the area that requires it, but that option F is the best otherwise. Option A always feels like I'm fighting the system, and often feels redundant, like I'm too stubborn to accept that I should in fact not bring Armor of the Fallen to fight the Jelly King. Attempting option E seems to be worse than just bringing normal weapons and not trying to beat the system, although Gran Faust charges can be used for many situations provided some level of immunity via my divine mantle w/ curse med, allowing some interesting hybrid options. I have yet to go with option G, but am looking for a set of UVs that I like on a drake scale shield to make into an omega shell. Option A seems to be good as well- boosting overall resistances is quite nice.
In the end it really depends of what you are looking for ... Here are my opinions, coming from someone who have lots of different gear so can adapt to the situation (obviously, someone who have only one-size-fit-all armor would have a different opinion. But that person should probably not look into UV in the first place) :
A) Seems like a bad idea. I actually got shadow on my Vog, and elemental on my Snarby, and I highly regret it. There are little situation where it is really useful to have both and the UV actually makes a difference. I don't have enough data to comment more, but even in FSC with shadow UV on Vog, I think I would probably not see the difference without.
B) In that case I would probably go Normal, since it's more generic, but there would be more beneficial things instead
C) That seems like the ideal UV : I looked into that, and apparently you need the full set + a low UV to get immune to a status from oilers (from that thread). The difference between immune and not immune is HUGE, and bonus : you only need ONE low. It definitely seems like the best price/effect option. For C42, if you are going for a specific set, Dragon Scale with a poison low and a fire low should make you immune to oilers status. I am currently aiming to do exactly that.
D) The Shock UV on Skolver is popular for a reason. Outside of LD, which highly warrants the usage of Shock UV, I can't really think of a use-case where you'd want an UV to cover weakness : you should get an armor that resists that status in the first place (depending on the status, it may be more benefical to resist the status than the damage. I'm looking at you, Shock). Unless you absolutely want a specific damage resistance and no armor of that damage resistance have the status resistance you want
E) I don't understand that question. If you meant resist curse, no it's not worse it. Either you have 4 weapon slots and don't care about the curse or you don't and just don't charge. Same goes for FoV, more or less, in my opinion (though it's more of a fun weapon than something you would really use for performance)
F) whatever have the less diminishing returns, so piercing med if your other part don't have piercing, otherwise piercing + normal. Assuming the diminishing returns is applied after additionning both of your armor, thing that I'm not sure about. And assuming that both are equal, which they are not since there is much more normal than piercing, as stated in B) (especially in T2)
G) UV's on shields don't make a big difference. You might as well boost an existing stat, since otherwise you are better served using another shield altogether.
Overall, I seem to agree with your conclusion.