Stormguard Warrior is an excellent feat – for building a character around

Stormguard Warrior can add huge amounts of attack and damage bonuses, but it requires that you be pretty dedicated towards generating attacks of opportunity to not take. Specifically, the feats Karmic Strike^CWar and Robilar’s Gambit^PHB2 are often used, because these feats allow you to take many more attacks of opportunity than you could otherwise (Karmic Strike allows you an AoO every time you’re hit, while Robilar’s Gambit allows you an AoO every time you’re attacked, whether they hit or not). Other ways of getting attacks of opportunity (defensive rebuke Devoted Spirit boost^ToB) or prevents others from avoiding them (thicket of blades stance^ToB as mentioned, Mage Slayer feat^CArc) are also useful, but don’t add nearly as much as Karmic and/or Robilar’s.

But Ironheart Aura is pretty much a dead feat, yes, and without Karmic or Robilar’s, you’ll rarely see more than +4/+4 from Stormguard Warrior. +4/+4 for two feats isn’t entirely awful, of course; the Weapon Focus/Specialization line (which are awful) is four feats for +2/+4. If you have reach and thicket of blades, the +4/+4 seems pretty likely; using defensive rebuke can improve that dramatically. And it is pretty much expected that you’re using Power Attack with a big two-hander, so it’s really +0/+12. Basically, you’re trading extra attacks (attacks of opportunity) for more potent attacks in general (skip one AoO, get a full attack with +12 on each attack). So it’s not a terrible use of feats. Just not the highly-recommended one that it would be with Karmic and/or Robilar’s.

Also, note the Combat Rhythm option on Stormguard Warrior; it’s not nearly as explosive as Channel the Storm, but it is cool. Personally, I have always wanted to have that opportunity to combine it with avalanche of blades for hilarity. That’s not really an option for a crusader with a warblade dip, though.

The other thing to point out about Stormguard Warrior is that the Evasive Reflexes feat^ToB uses the same “don’t take an AoO you could have, get something instead” mechanic, and like Stormguard Warrior, it doesn’t use up the AoO. You can use both Evasive Reflexes and Stormguard Warrior. This is particularly useful when you have thicket of blades – their 5-ft. steps provoke an AoO from you, which lets you 5-ft. step to keep up with them and gives you +4/+4. If that step was to try to get away from you so they could do something that provokes (say, cast a spell while you have Mage Slayer, or attack an ally after you hit them with defensive rebuke), you have either just prevented them from doing that, or are going to get pumped up even more.

All 3 games mandate making attacks from highest base attack bonus to lowest

Player's Handbook (2000) for Dungeons and Dragons, Third Edition on Full Attack says

If you get multiple attacks based on your base attack bonus, you must make the attacks in order from highest bonus to lowest. If you are using two weapons, you can strike with either weapon first. If you are using a double weapon, you can strike with either part of the weapon first. (124)

The Player's Handbook (2012) for Dungeons and Dragons 3.5 on Full Attack says

If you get multiple attacks because your base attack bonus is high enough, you must make the attacks in order from highest bonus to lowest. If you are using two weapons, you can strike with either weapon first. If you are using a double weapon, you can strike with either part of the weapon first. (143)

In the 4th printing of the Pathfinder Role-playing Game Core Rule Book (2010) the latter is repeated verbatim on Full Attack (187).

Thus, without further guidance, it seems reasonable that the player picks the order of his character's attacks if two or more attacks are tied for the same base attack bonus (such as when wielding two weapons). The player, however, can't pick the attacks that are made at less than the base attack bonus (e.g. the additional attack at +1 from a base attack bonus of +6) until after attacks have been made at the full base attack bonus.

The example D&D 3.5 character with a base attack bonus of +6, the feats Two-weapon Fighting and Improved Two-weapon Fighting, and affected by the spell haste taking the full attack action makes 1 attack with his primary weapon at his full base attack bonus, 1 attack with his off-hand weapon at his full base attack bonus, and 1 attack with either weapon at his full base attack bonus, and the character could make those attacks in any order. He then makes 1 attack with his primary weapon at his base attack bonus −5 and 1 attack with his off-hand weapon at his base attack bonus −5, and could make those attacks in any order.