While his Guardian Shiled effect is up at QS, the party lacks shields to prevent HP damage. The enemies also don't have WoL's Lock debuff at wave start so you can either:
Shining Shield (S1) to protect the party in his Shield
Throw Buckler (S2) one of the enemies to start taking BRV hits on the enemy turns or
Bitter End to apply shields AND apply lock to all enemies in one swoop.
Most fights won't need you to go through all 3 LD uses thanks to Guardian's Shield's duration so feel free to still open with LD!
With enemies locked on you, expect to Throw Buckler to refresh just your shield when needed. You also get a 3T Elude buff that may help you dodge getting debuffed. This is otherwise useful to shave a single target if the EX is not charged.
Shining Shield is your bread and butter for protection. Pay attention to your allies’ shield values (light blue number when applying and being attacked) and make sure to refresh when they get low.
Shining Wave (EX) is his minor source of healing for the party. It recharges in 2 skill uses, and WoL isn’t particularly fast so he’s fine to spam skills!
All Resist Up is extremely useful if you know a big attack is coming and you’re worried about the shields getting shredded.
Ultimate Shield (BT) gives him access to more aura buffs to strengthen the party without needing to use his Burst Phase allowing your main damage dealer to go all out!
Soul of Light (FR) is very simple and effective as it asks for:
Anyone to reduce/absorb BRV DMG (40%) which his shields cover
Act with WoL's shield buff on party (10% per ally, 30% max)
Warrior of Light attacks someone targeting him (20%)
On-turn increases may seem small (30% for allies, 50% for himself) but his off-turn increases being 40% if he just does his job of shielding is huge especially paired with a trap/counter unit to take advantage of these increases.
If the attacking ally has WoL's shield during his Force Time, that's a whopping 50% HP DMG and Limit up to their attacks!