Agility and Stamina

This alpha power seems much better than Cardiac. Would choosing this power be worth it if the only endurance type power is Stamina? Does it affect IOs such as Numina/Miracle?

I'm thinking of more Melee type ATs.

Actually the end reduction from Cardiac is better than the end mod buff from Agility especially when it would only affect Stamina. While the end reduction in Cardiac will affect all your powers. So therefore it comes down to defense vs resistance and which is better for your character, but you didn't ask for advice about that. Agility will not affect IO's.

Mr_Body is right: Cardiac will be a much greater help with endurance issues than Agility, especially if it's only affecting Stamina. Agility is great for the defense and recharge, but Cardiac and Vigor are the best alphas for solving endurance woes.

I took Agility on my Time/Electric defender mainly for the defense and the recharge. The End Mod is also good for the end drains in /Electric, but doesn't do a whole lot for Stamina. My end bar goes down pretty fast, but between Chronoshift (which is affected by Agility) and Conserve Power I almost never run out of end.

If you're having end problems Agility will probably only worsen them by adding more recharge.

Agility will only really help your blue bar woes if you have a power like Accelerate Metabolism with a large-scale recovery bonus for it to boost. In that situation (especially because AM has a long recharge timer) Agility is awesome. For the vast majority of characters, though, Cardiac is your go-to if you're sucking wind. Some builds may prefer Vigor, too, especially if you slot lightly for accuracy or have multiple powers which benefit from the Heal modifier (though the big ones there, Regen, Willpower, and Empathy, don't particularly struggle with Endurance management in most cases).

I24 Proc Chance = (Enhanced Recharge + Activation Time) * (Current PPM * 1.25) / 60*(1 + .75*(.15*Radius - 0.011*Radius*(360-Arc)/30))
Single Target Radius = 0. AoE Non-Cone Arc = 360.

My main is a elec/elec brute and I use Cardiac, I have most of all the other Alpha's unlocked to tier 4 and still think Cardiac is a great fit even on a alt that has no big endurance problems and has power sink to refill end.

The end reduction is great it really helps out by saving slots or focusing on other enhancements for powers. Even powers like a damage aura you can get by with a little end reduction with cardiac and be fine. The extra slots I save I can use to max out defense with set bonus.

At lower levels it can be a problem but nothing that blues or watching your power usage cant handle.

If you are looking for an alternative to Cardiac, you might want to look at Vigor.

what I like about agility is that its +rchg is offset by its +rec, so I your build works well wihtout it, the extra rchg will not kill you.

Great responses so far. I will just chime in and say that I initially thought that I could run Agility instead of Cardiac on my grav/time, but unless there is someone else juicing my blue bar, I can run myself dry. Though the + Def and +Rech are so good that I routinely swap one for the other on that toon.

That's one thing I love about incarnate powers! you can swap to suit your needs!
I routinely swap Destiny.
I've never tried swapping alpha, but based on this discussion I've decided to make me Cardiac to try in my inv/SS tank so I can compare the tow (I'm quite happy with Agility, but I don;t have an End issue without it either)

It should also be noted that agility will also improve the end drain on ion radial judgement, and the recovery buff from ageless core destiny. I'm unsure if it affects the end drain from preemptive interface, but it might. The ageless is the important one, though. Even at it's lowest point it gives +100% recovery, which would become 133 or 145% depending on which agility you have. That's a pretty big increase, probably more than enough to offset not having cardiac.