Well, with that premise in mind, I'd first wonder if you want more tanky or more DPSy... I am assuming that with orc, you'll do the right thing and go for a musclebound stamina build instead for a weak-wrirsted magica caster... strong and tough kinda is the orsimers stock in trade after all

You could go for an juggernaut style with heavy armor or for berserker style with medium armor.
Former will be very effective, your dragon blood will likely be more then enough to heal all that gets past your armor, but you will also likely run out of stamina all the time and need to use a good deal of heavy attacks.
Latter may require a bit more skill to pull off well... but your weapon damage output and stamina regeneration will be nifty.

Weapons... since dragonknights have no universal gap closer of their own (chains don't count, since they can only pull the ones not CC immune) you likely will want to avoid dual wield and go for two-handed and/or one-handed&shield. Both will work very well, if you like DPSing I would say 2H has a slight advantage... also, fits the orc mindset all the better, just grab the biggest axe or mace you can find and go oput to bash heads!
Secondary weapon... can either be the other of those, or bow for those instances where ranged attacks would serve you better. Dragonknights make fearsome ranged opponents, since their flapping wings make them practicaly immune to most ranged stuff, so they tend to win most archery duels...

AoEing... your standard of might is a nasty one, burning breath is fun to use, and if going 2H, the cleave will likely see much use too - short range AoE with shieding effect? What's not to like? The talons too will be nice, especially if you go with a berserker build that depends on mobility rather then just barreling through opposition.

Soloing is something DKs excel at in any build, having a nice in-combat selfheal with dragon blood and lots of "stand and fight" abilities. Again Standard of Might is a neat one, AoE and increase damage done, AND reduce damage taken? In all too many encounters, plopping it down is the "I win" move (since enemy mobs usually aren't smart enough to avoid the nasty area).

Tanking... DKs have a lot of "armor up" abilities that can make them somewhat tankish even when not wearing heavy armor, and the best tanks when they do.

In the end, finding out which combination works best for -you- is part of the fun! And if you keep at it... well, there's lots of skillpoints in the game, kore then enough to learn and morph all your class skills and essentials... with many left over. You could easily level up both armor types, mix them, and then swap as you like for the job at hand...

Hmm for me and my DK tank build volitile armor morph from spike armor is good gives good armor and spell res for 20 secs and damages enemies for 10 seconds that are near by and reflects damage back to melee attackers be it small though. For DPS and a general good skill that is nice is burning breath firey breaths morph changes to stamina cost and scales off weapon damage deals good fire damage and DOT damage (be though DOTs aren't good to begin with) and best part reduces targets armor by 5,000+ for the duration.

Green dragon blood that's a must and Corrosive armor morph of magma armor the Earth heart ultimate caps damage dealt to you at 3% and gives you 100% armor penetration and deals fire AOE damage to any one near you. You could try magma shell it's other morph which allows allies to activate a synergy that grants them a damage shield that covers there entire health bar bbuutt the litteraly have to be clipping through you to activate it and that's if there lucky enough to get it in time since it only appears for a second or 2 and the shield it self only last for like 3 seconds.