* Does it resist for a fixed amount irrespective of enhancing skills?
-- Very probably not. We know that both potency and duration depend on skill for bar-element spells, so it is probably the same for status spells.
* Does it scale (linearly or otherwise) with enhancing magic to the previous enhancing cap of 300? Does it scale to the new cap of 500?
-- It likely scales to the cap of 500. If you look at the duration equation, it doesn't even take off from the floor until something like RDM's level 72 skill cap. As far as I know, the equation was added when they raised the cap to 80. If they were going to add a new duration equation, why would they not add a potency equation as well?
* Does say, bar-paralysis reduce the % chance of being paralyzed? Does it even effect the potency of the ailment?
-- It is almost certainly magic evasion and has no effect on potency. Barsleep does not reduce sleep duration or make you any less slept. Barbind and Barsilence are two other that can't even decrease potency. You could test this with Barblind the easiest. I assume it is magic evasion because Barstatus spells are incredibly useless in some places (think of casting Barsleepra when fighting mandies in Kazham) but very useful in other places (see below) which is what one would predict if it was Magic Evasion.
* Is there an efficient reason to even use them in the first place? (with the exception of bar-amnesia; as it seems more efficient to cast the appropriate -na) -- I use Barparalyra when fighting Reinforcement monsters in Salvage. Combined with Barblizzara, I can generally melee them to death with 1-2 Ice Spikes paralyze procs at most. Flooring ice spikes proc rate like this makes the frequency of paralyze from it worth Paralyna-ing, unlike when it is a near-100% proc rate before buffs.
* Do the bar-element spells have a
greater chance of reducing or resisting elementally attuned ailments rather than the appropriate bar-ailment spell?
-- This would likely depend on their relative potencies, which there has been no testing (that I know of) on.
* Are bar-ailment effects multiplicative or additive to bar-element spells?
-- Additive probably, in the most direct sense (adding magic evasion) as far as their effects on resistance, it's going to be something more like the left graph on this
page. When you add magic evasion, you are moving yourself from the right to the left, which means "no resist" situations are less likely to happen down to whatever the floor is. If you had a 50% resist rate on a 1-state (linear) debuff with the Bar-element spell and then you stack the bar-status spell on for another 50 MEvasion, you will reduce the land rate to 25%. If you look at the graph a little harder, you can see that for 2-state debuffs like Sleep (or 3~4 state ones) this would be an even more dramatic effect.
* Are bar-ailment effects multiplicative or additive to Resist {ailment} job abilities?
-- They are very likely separate. When Resist traits proc, they say "Resist!" in the log. This proc rate appears to be independent of monster level vs. yours and pretty much any other factor I can think of, which is very different from the Mandy example above. You also do not see any "Resist!" messages when you are resisting stuff with barstatus spells.