On redelia Build you dont really need a botrk because you have lot of sustain and tankiness. I know that botrk do max health dmg but dont help with frontline aspects. Armpit lover is a build where is up to you if you want to build or not botrk. I just dont need it because i have the sustain from the other item as spirit visage that amp your q healing among revitalize rune. In that build (armpit lover) you dont even need attack speed because you already have a trinity that provide mithic passive. If you have more doubt ask freely. GL!