I think you'll find that a lot of people carry the swedish firesteel or the Kershaw product for the same reasons you've mentioned. I never thought the extra bulk of the magnesium was a detriment, but then again I've never actually used the magnesium for firelighting. Like you said, it tends to blow away and when you finally get it to flare up, the flame may not last long enough to ignite your tinder.

It's also mentioned that the Doan product is superior to the Coghlan's and other clones - as evidenced by the relative ease with which you removed the rod from the block. The lesser ones tend to separate if dropped.

I find that something with very sharp 90 degree edges, like an SAK or leatherman saw spine is the best striker. I wouldn't worry too much about wearing it down, with practice you'll aquire the right touch and the rods are cheap anyway.

I would say that rod diameter isn't hugely important. After all, even with a 1 inch diameter rod, a square striker is still only going to contact a very narrow strip of the ferro. If you've got good tinder, like a vaseline cotton ball or lint, the Coghlan's sized rod is even overkill.

Instead of the shavings, I would consider smashing up a trioxane bar and carry the powder in a straw for when you really need fire fast. It lights easily with a sparker and burns hotter than cotton and longer than magnesium. You should be able to get a three-pack at the army navy store for 99 cents.