I could make the Willowisp boss to be rare via min time required for respawn AND X number of low level wisp to be killed since the zone goes up. The min time can be min time for zone to be up plus min time since last spawn/kill. Some type of forumla to allow 1-2 spawns per day, very rare, can't predict when it will spawn, and can't just sit in zone, need to kill trash.
For the OT zone, I like the idea of Stonewall/SpellDmgReduction Buff. Could make it a 3 tick bard buff that can't be dispelled and constantly refreshes via player.pl script in the zone so when you zone out you don't have that 3 tick buff anymore. Would need to make sure warriors don't get over 100% stonewall, so maybe they would be excluded and just give that buff to non Warriors.
As for the spells being resisted, we can make special pvp spells that have 0 checks on them, so they always land, no matter how much resist an enemy player has.
So seems we have some potential here.
I would suggest that one spawn be static and the other be random. In example: Wisp might always spawn at 6pm EST and then once more randomly between 7pm EST to 5pm EST. With a single, static spawn you give players more time to prepare for it. If I were in the middle of a T5 clear, I wouldn't bother stopping what I am doing to log in an alt or break my group up for a sec to go chase after a 2-3mil. If I knew that it was ~90min until the 6pm spawn, I might speed up or slow down to prepare for it.
Bard ticking buff is nice. I was considering an unlimited, but that works much better. To make sure players don't overcap, simply remove & block any spell with effectid 168 or 161 (SW or spellmitigation) excluding the OT Stonewall.
For the SpellResistChance, just tack it on to the OT Stonewall. effectid = 126 and effect_base_value = 50. It takes a whole percentage point for the base value, so 50 = 50% resist reduction chance. Players with UW would still have HUGE advantage due to HP and 50% chance to simply not be hit by spells.
As for adding special spells, I would avoid it as it's simply more work, more spells, more situational stuff. In my flawed opinion, I would suggest keeping things simple and tack on the SpellResistChance instead. It would be more scalable too if it's too OP or too weak.
-Hate