Rapid Shot: Occasionally quickens Ranged attack. The time being cut is based on the Ranged attack time, i.e aiming time will always be fixed and cannot be reduced. This ability is similar to Conserve MP of Black Mage, i.e it is always active, and randomly cut the Ranged attack time by a percentage, which should range anywhere from 0% to 100% (instant firing).
There are only 4 pieces of gears which can enhance Rapid Shot, of which only 2 can be used by Ranger main effectively: Hunter’s Beret and Scout’s Jerkin. In order to justify the use of those 2 pieces, it is best to compare with the maximum increase in damage if you can switch to use other gears. Assuming ranged accuracy is not a problem, then, in this case, the best you can get would be: Wyvern Helm +1 and Kirin’s Osode.
Wyvern Helm +1 and Kirin’s Osode give 16 more STR in total, or an increase of 8 in fSTR2, and 8 ranged attack. Now, for the sake of simplicity, let’s argue that the increase in ranged attack is not significant enough, so pDiF is the same. With a Base Damage of around 125-140 in most cases, that means I am sacrificing 8/~125-140 = 6% of damage per shot.
So, thought #1: If Rapid Shot from Hunter’s Beret and Scout’s Jerkin can increase the activation rate (adjusted for the actual time cut) by more than 6%, then in TP mode, it is better to use those 2.
The argument is of course flawed in many sense. One of the reason could be that if you use Osode, it facilitates the switch of any accuracy ring for a STR ring, which would further improve your fSTR2. But in most cases, I found that to be able to get 90-95% ranged accuracy reliably while using meats, it is best to use both Behemoth Ring +1 in ring slots, so it is not really a good argument.
What I have found from being in good party, or in a good LS, is that usually, I don’t have enough time to shoot much to see the increase in ranged damage constantly. Take, for example, if I wear Osode instead of Scout’s Jerkin, rarely I could get a 2nd shot of any Dynamis monster in my current Linkshell. But if I use Scout’s Jerkin, I find that more often that not, I could get a 2nd shot of near the silver health of the monster. It comes into my thought from being in party with Rukenshin that, no matter how high my single shot is, if I can’t keep up with his TP, I will never be able to put my damage anywhere near his damage, since what I can do better than him is my spike damage from Sidewinders. Also, it is always better to get an extra 15TP before monster dies than getting a maximum of 24 extra damage per shot over 400 damage per shot (pDiF = 3 case). It happens a lot in MNK burn party, when my Ranger has to keep up with them in TP, since they have the tendency to kill monster when you are aiming hopelessly wishing that your arrow hit before they actually finish the monster.
Unless SE gives Ranger some sort of Haste, I put trust in my Rapid Shot. It is situational, but it is nevertheless one of the useful ways to put you on par with some other melees, especially the ones who can access enough Haste to rely on TP spam (note: WAR, SAM, MNK, DRK).
More tests need to be done – I hope I can get a party this weekend!