Skill Discussions

Yes, the cap usage increases.

The skill's not (completely) detrimental because that duration it decreases has to do with the shifting of the resists to match incoming damage. So with higher levels it shifts resistances faster and uses more cap.

You will be receiving much the same damage, but it still takes time for the reactive hardener to react and to shift from it's default resists. Higher the skill, faster that shift will happen (but more cap it'll use overall)

Because the RAH is stacking penalized with DCUs and not normal hardeners. So if you are flying against say Guristas with an armor tank you will get more kinetic resists from a kinetic hardener and a RAH than two kinetic hardeners.

Its also nice for Dread Pirate Scarlet.

I've always used two of the primary damage hardeners and one of the secondary. I guess it would depend on how fast it could change resistances to determine if it was worth it. I understand it will give you 30/30 or 60 percent but that's after it fully changes. How long does that take with the skill trained to level 4?

Interesting.... From my calculations it would take 30 seconds for the 30/30 resist if the 6% is for both resists at the same time and 60 seconds for the straight 60 percent resist. This is with armor resistance phasing to 4. I will try this on a Paladin I plan to set up for missions.

The module is designed to be used on Battleships and higher, ships that would not care about the capacitor usage, anyway.

Some Gallente and especially Amarr pilots can make fantastic use of the reactive hardener and I try to explain some viewpoints as well and short as I can.

You fly an Armageddon in nullsec, running combat sites and highly ranked anomalies with it, for example Sansha Haven and Sansha Sanctum. When you warp into the site, you have to tank a lot of initial damage coming at you, and having the skill trained to IV, maybe V, will help you by a large margin to reach the 60% EM resists ASAP. In combination with 1-2 EM, and 1 Therm Hardeners you will be able to reach 90% EM resists and tank the sites with ease. Maybe you only use EM hardeners instead and therm rigs. But all that is a matter of trial and error, seeing what EM/Therm resist combination works best for you.

Consider that the reactive hardener does not stack with the other hardeners you use, afaik, please correct me on that if I am wrong. DCU is not needed in PvE situations.

While you fight the spawn, you can turn off the reactive hardener at some point, when you feel that you can tank the damage with your other 2-3 active hardeners and recover some cap, if you have capacitor concerns, but really, this should absolutely not be the case.
With each new spawn of rats you turn on the reactive hardener and "übertank" safely again up to the point where you can turn the device off. Due to the devices quick adjustment to 60% EM resistance by having the skill on IV or V you can freely turn the device on and off without "wasting resistances" to other 3 damage types for too long if you wish.
You basically turn the module on and off like a armor repairer that you only keep running when there is armor damage to repair.

Having the skill on level 1 or 2, possibly even 3, will put you in the situation where turning off the module and reactivating it might cause you to "waste" resistance stats on unnecessary attributes for too long, thus take unnecessary damage and basically render the module as "worthless", thus you might feel forced to keep the module running, even though the 60% EM resistance were not needed, thus wasting capacitor anyway. Consider that during the time, when the module is adjusting to its optimal tanking value of say 60% for a specific damage type, it can be plainly considered as "underwhelming and way beneath of being worth it".

The reactive armor hardener is pretty cheap and offers desirable resistances for its price. You can treat the device like a DCU for Armor, which does not stack with your other armor hardeners, just like the DCU.
However, the DCU is basically a Hull-tanking device with shield and armor boni. The reactive hardener is for Armor only, thus way more efficient if you are only focusing on armor tanking.
And because you are active in a PvE environment, you do not really need a DCU to buff your hull, for you won't ever get that far.

Basically, if you fly a Battleship or higher with no guns fitted, using drones, or having guns fitted that do not drain capacitor, or missiles, and you have strong capacitor skills and module setup and want to replace the DCU by the reactive hardener, because you do not expect to ever have the need to tank any hull damage, then this item is a very very nice tanking item for an affordable price.
Only officer hardeners would offer you similar tanking, BUT be penalized with your other active armor hardeners, and even cost 200+ mill ISK. The reactive armor hardener does not even cost more than 300k ISK and does not suffer from stacking penalties! And it offers you 60% resistance!
Just think about this.

As a matter of fact, the higher you train the skill, the more adorable the module gets. Of course you should not be heavily capacitor reliant, preferably using weapon systems that do not use capacitor.

I personally would not hesitate to train the skill to 5, to be honest. I do not need the skill to 5 right away, level 4 is sufficient, but later in my career this skill will definitely go to level 5 and I know that I would not regret it.

You only turn it off to reset the resists to 15% rainbow, otherwise you leave it running.

When doing missions, I only run it when I am taking armor damage to save capacitor, but otherwise I ignore it and let it run continuously.