My point was that by strenght itself you cannot get hits that ID toughness 4, thus stacking the strenght isn't worth it.
And also worth noticing that i comment practically from my local metas point of view, where toughness 5+ is a true rarity, yet alone T5 with multiple wounds. I think i've played once against bikes. I am only one with ogryns, no nids on our games. Only things with higher toughness are those that eldar and chaos space marines (+ daemon allies) can produce, so basically wraith construct (no wraithknights seen yet) and daemon princes what has been on the table..