My 320+ defense and 4.2K HP WoL almost die in an instance.
If you have shining splendor just use it and hope it'd blind him for a while.
Fifth try, and a ton of experimentation, and a crapload of luck, sent the Hell Rider back to Demons Unleashed hell for the last time. Good riddance.
Right now, the fight is an absolute crapshoot. You either have to land a highly resisted blind or power break to have any chance of winning greater than 0 percent. The window of opportunity to land either of these before wiping is very small.
Swapped out all physical DPS for a pure fire mage team + tank/healer (ran with Terra/Tellah/Kefka/WoL/Lenna). Better damage, and a 2nd raiser really helped, but still would have wiped easily had Terra not somehow landed a random power break on the Hell Rider. With a power break, its damage was reduced just enough to be manageable and not one-shot everyone that wasn't WoL.
Everything, as expected, went to hell once break expired. But, at that point enough ticky-tack damage had accumulated to the point where I limped over the finish line (which was convenient, as I would have total wiped after that turn).
At this point, I'm reasonably sure that the S-2 boss is balanced around having a 6* Cecil to tank it. Right this second, there's nothing really out there that can maintain a sustained encounter with it safely.
If you say WoL is mediocre at 5* then Cecil is trash. At least my Wol has 5.5k hp and I haven't found anything that could even make a dent in him. I see your point about utility but WoL is still amazing at 5* and I haven't lost a single fight with him in the party but then again I kill mobs in A-3 with my mage party in 2 turns and none have died so far/
Wait until you get to S-tier. You'll eat those words quickly once you encounter common monsters that hit your mages/healers for 3000 physical damage. No cheezing with elemental resists here.
You will totally understand WoL's weaknesses in his 5* form all too well when you get to the Hell Rider in S-2. 5500 HP is great and awesome. But, can you keep him up while he is enduring 3000-3500 damage every single round while maintaining any damage output at all? If so, what happens to your healing supply line to him when Provoke from Golem fails and the Hell Rider one shots someone in your party?
Oh... and by the way, the Hell Rider gets 2-3 chances every round to bypass WoL and one-shot someone. How many rounds do you think you can last before Provoke misses and you go instantly from a controlled encounter to a complete wipe in a single round.