I think the current Dragoon Helmet is really well done. 2% SP costs per second sound like much but it’s not if we consider the low SP pool of Swordsmen and the fact you can use an Alchemist SP potion every 15 seconds which recovers up to 2576 SP.
A normal Swordsman without any SP increase quest items/collection/equipment/title effect has ~4320 SP at lvl 390. Let’s say we give him a few collections & titles and increase that to 4500.
This means the Dragoon Helmet will drain 90 SP per second, or 1350 over 15 seconds.
This means it drains about 52,4% of an Alchemist lvl 15 potion away.
However, in the same time the Dragoon already recovered ~ 100 SP via natural SP recovery (if we average 3% of max SP over 20 seconds), so we’re looking at a net loss of ~1250 SP vs a recovery of 2576 via the lvl 15 Alchemist SP potion.
If we average that per 30 seconds so we can include the NPC potion, which recovers another 1834 SP every 25 seconds, we have a total SP recovery of 6986 SP via pots vs an upkeep cost of 2700 SP for the Helm, leaving you with 4286 SP to spend on skills.
To bring that into perspective, that’s enough to cast:
37 x Dragon Tooth
35x Serpentine
36x Gae Bolg
57x Dragon Soar
38x Dethrone
28x Dragon Fear
or 26x Dragon Fall
Even if you spam all Dragoon skills like a madman you will not run out of SP, and even with two other Classes and skills to spam, I seriously doubt that you will ever run out of SP.
And if that is the case, you can simply make the helm lightweight via attribute and reduce the SP consumption accordingly.
The only case in which Dragoon is is trouble now is if he stacks too many max SP increase items/effects, which drastically increases the number of SP drained per second.