True, but that ship is there through "unnatural" means, it can only survive in the warp due to protection from it's geller field. Draigo was cursed (or blessed) with the ability to wander the warp like he belongs there as opposed to the material realm. That has never happened in the fluff before (at least to my knowledge) so how do we know what will happen?Well look what happens when a ship's geller field fails whilst travelling through the warp... It's doesn't exactly result in "order" being introduced into the "chaos".
We know almost nothing of what the Emperor has done in the warp, making that a weak argument. Hell we know more of what Magnus has done in the warp then we do the Emperor.Regardless of how he ended up in the warp, his exploits seem more impressive than anything we know even the Emperor himself has done.