User blog comment:Linathan/Unit Spotlight: Ruinous Despoiler Galtier/@comment-24570336-20161101085752/@comment-24570336-20161101142655

Galtier's BB/SBB will either deal their normal damage or 5% of enemy Max HP, whereas UBB will deal its normal damage modifier and 5% of enemy Max HP, as written in his unit page.

I do think Galtier has useful skills for Arena, but they may become irrelevant if his skills just suddenly ignore offensive buffs while being the only unit left.