Is there any significant difference in time using a shield vs using a weapon to block? It feels like my character can block with a weapon faster than they can raise the shield and block. Maybe it's just me.

I typically play through using a sword and shield, 'sword-n-board' I think they call it. After watching the Alliances trailer for TES Online, I played as a Nord who carried a two-handed axe and wore iron armor. I was able to block much more easier and better. It just felt faster than a shield. I could block practically any melee attack!

If I use a shield, I always end up timing it 'too late' or something and most of the time I fail to block the attack.

I think if it is the case it makes sense, as a shield must be heavier than a weapon, so it would be true to reality.

Also, as a balancing measure:

Blocking w/ weapon = faster but less protection

Blocking w/ shield = slower but more protection

Seems very sensible too.

That may be true, but I always saw the balancing measure as using a shield meant more protection, but your weapons deal less damage. Blocking with two-handed weapons would increase damage, but lower protection. Dual-wielding has no protection but massive damage. I don't think wielding one one-handed weapon was really thought of.