From my limited experience:
Warblade's a great heavy-hitting melee character all on its own, but if you multiclass, take it later. You can count earlier levels as 1/2 your warblade level for what level you get access to maneuvers, though your first stance has to be first level.
It supports single devastating attacks somewhat better than large numbers of attacks, but can do both. Look for boosts rather than strikes if you go with a martial character and want a lot of attacks.
With a 2-handed weapon, Power Attack gives better output. Look into the feat Shock Trooper from Complete Warrior to take the hit to his Armor Class rather than Attack Roll, but he can't do that until 6th level. Warblade's Emerald Razor's worth taking despite being a strike for this reason... but that would be a single, devastating attack.
If you meant two-weapon fighting yes, that does suffer badly against DR. Transmuting weapons (+1 bonus, magic item compendium) can help with this however, as does just dealing enough damage with them. They however suffer from not being able to Power Attack well since Power Attack doesn't work with light weapons
except natural or unarmed.
Consider natural weapons as well. If you have claws, you can use
both of them as a primary weapon, getting full Strength and attack bonus. Unless you got them from being a psychic warrior, should you get more natural weapons, you can use them as secondary weapons at 1/2 Strength and a -5 penalty that can be entirely negated should you take Multiattack and Improved Multiattack.
My personal favorite build involves a Changeling Warshaper with 12 or so tentacles shaped as primary weapons and disguised as hair braids, but you may wish to avoid such things...
Ways to get natural weapons involve 5 levels in Druid or in a Ranger variant for Wildshape, 2 levels in Totemist, a level in Warshaper if you're shapechanger subtype, casting Alter Self, Polymorph, or Metamorphosis, being a Psychic Warrior and using any of their powers to get such things, being a kobold (Races of the Dragon web enhancement), being a lizardfolk, being Feral, and ... well, a variety of means.
Non-spell ways to enchant natural weapons include the Kensai prestige class from Complete Warrior (if of a single type, much cheaper than they would be if you tried to enchant that many normal weapons!), Thayan Gladiator prestige class (from... Champions of Ruin I think), Amulet of Mighty Fists (expensive), and Necklace of Natural Weapons (Savage Species)
Good sources of bonus damage are Sneak Attack (sometimes, get a pair of deathstrike bracers to mitigate the problems), Boosts from Warblade or Swordsage, being inspired by a bard, getting Greater Magic Weapon cast on your weapons, having a decent Strength (Power Surge from Kensai or Rage/Whirling Frenzy from Barbarian can help), Power Attacking and mitigating the loss of attack, Leap Attacking along with that and getting a full attack at the end of the charge (Lion Totem Barbarian from Complete Champion), and a variety of other things I'm sure someone else will be happy to explore.
