Is Elemental Protection and Deflect Arrows, from the Block tree, really all that important if you're heavily invested in Armorer+Heavy Armor (arrows do less damage) and Enchanting (elemental defense)?

I am torn between Sword+Board and Greatsword. As stated I will travel deep into Armorer+Heavy Armor and Enchanting, so with all those bonuses, I just can't see the need for a shield. So I'm wondering what other who have played think.

If you plan on using a shield at all I'd get them.

I'll be getting 4 points in block (up to block runner) pretty early, and I'm going DW. I expect I'll be using 2 weapons 80+% of the time, but there are occasions when it just doesnt make sense. Against archers and mages, i'm certain i can kill them in a couple of strokes with one weapon, I just need to get to them alive first. A shield will let me do that.

Even if I only end up DWing 10-20% of the time because blocking with those perks turns out to be way more viable, I'll only have wasted 3 perks on DW.

Using a shield in this game looks to be pretty darn fun, if you look at the Block perk tree.

The ability to bash and then upgrade to a bash that does FIVE times damage is very useful, then the charge that you can do sprinting with the shield raised and knock down enemies like they are bowling pins, nice!
Then you can defend against arrows, any arrows hitting the shield does ZERO damage and you can protect against magical attacks with 50% mitigation as well.

I usually never play with shields, but this game makes me want to do that.

Personally that says a lot to me.

Basically this. I actually enjoyed Oblivion's melle combat very much, but when you boil it down, sword and board really is just *block* ---> *swing/swing/swin* ---> *block* ---> *swing/swing/swing* ---> *block* and so forth. The diversity came in trying different playstyles with the same character, not from any one style of play (maybe straight mages).

This time it seems like between the different perk effects for one-handers (like extra bleed dmg with axes) and all the different things you can do with a shield (the final perk where you can charge and knock people over is just fantastic), sword and board looks to bring almost as much combat diverstiy to the table as every style of melee comabt in Oblivion combined.

What I mean is, with high defense and armor enchantments, do I lose out in the long run if I go two-handed? Or is Elemental Protection/Deflect Arrow that broken?

Two-handed is viable, though there's certainly a defense tradeoff compared to 1h+shield

One possibility is to complement your defense with defensive spells (Oakskin etc), and focus on health, and you should be fine. Elemental resistance enchantments or trinkets can go a long way too.