The extra Def is nice, getting doubled is somewhat mitigated by Urvan and he'll be doubling with QR anyway. But I'm still not convinced these are his best IVs, or if they are better than neutral.
So, which is better? Should I look for other IVs or is +def -spd his best?
-spd, and he doesnt want to double at ALL. Doubling means his weapon effect is useless outside of brave weapons.
Things Bike wants: warding/fierce/steady breath, Renewal, Vantage, Cancel Affinity, Guard, Wrath, Mystic Boost.
Things Bike DOES NOT WANT: Quick Riposte, DC, Fury, Player Phase skills, Tadept, Blade skills.
B.ike speed tier is interesting. If you plan to invest in him then you won't want -speed. He can avoid a lot a doubles against other similarly tanky or sluggish units. If he doubles or quick riposte then aether will go off every enemy phase (assuming breath skill). +def will be vastly superior at base and lower merges. Most boons work on him and the bane is res since if he does get doubled by a mage (urvan kicks in). Can use hp if you're worried about getting one shotted. Being slow will only activate urvan in player phase, take reduced damage from second counterattack. In enemy phase he would attack back interrupting the opponents attack (urvan fails to kick in). The role you have or playstyle will dictate his ivs more. He can play as a pure physical wall or become a self sustaining bruiser.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes