Grotus, very nice data. I was going on the 4s listed in Warcry. The rules then are 65mph base, going up to 130mph for 5xSO.
The endurance thing is not much of an issue when you slot for distance. If you 5 slot for distance, its 200yds per port, or about 9 ports per mile. The map at worst is around 2 miles, or 18 ports. If you are chaining, thats about 1 min. The burn rate of 3.6eps v. 6slotted stamina at 2.9eps means a drain of 0.7eps. So the time to drain out your end is 100end/0.7eps, or 2min20s >> the 60s you need to chain across any map.
In fact doing 6slots in range probably can work with enough stamina slotting later, since you would then drain at about 1.83eps and burn out your pool in 55s, which is probably easy enough to clear a map. But the gain from that first end reducer is so big that I would rather have it and run a few extra toggles. I certainly would do this with unstoppable, since the eps gain from that is huge.
For refernce, when my invuln/fire tank had 5xrange in port w/SO's, it was 6 hops from the Brickstown metro to Creys folly entrance, which is 18s by your estimate of activation time.
Ill toss in a bit more here. I have been rooted while in unstoppable. If all I had was the jump, superspeed, or flight pools, I would have been stuck. Port lets you move around while rooted, which is a big plus in my book.
There are many uses for the prereqs.
Recall friend can be used to move corpses, move allies to your remote place letting them bypass stuff, and even be used by controllers to port pets to the exact spot they want. The uses for this power are clear.
Port foe is also very useful for a tank. It is really long range and non line of sight, which lets you aggro stuff from a fighting spot of your choice. You can therefore pull while denying LoS, forcing the enemy to say close to you through a choke point. You can also use port foe to pack in extras in your invince melee radius for not only the defensive bonus, but also the parallel killing via AEs. I have used port foe to aggro additional groups of mobs while I am tied down with one group, to help gather an entire room onto me. This power is useful to pull stuff out of solid rock and buggy maps...if you can target it, you can pull it out subject to the restrictions. Even the restrictions on porting can be useful. For instance if you want success, you go for minions (useful for packing), but if you want to aggro the entire pack, you go for a boss or a LT and even though you are guaranteed failure in some level situations, the aggro you generate can get you the pull of the whole pack.
I would argue in the context of an unstoppable tank, there is no better compliment for superspeed than teleport. Fly and its prereqs do not do you much good unless fighting in the sky is your thing. You dont really need combat jumping or acrobatics with the state defenses of unstoppable, and well sloted port would clear anything those could.
For invince, port is a very safe movement. This is because you can port into a mob cluster for high +DEF from invince, then port into another mob cluster to aggro that, and maintain your DEF bonus the whole time. Moving around by running will change the number within melee distance and vary your +def rating. SO as far as gathering goes, port is hard to beat- port to a cluster, port to a cluster, port to a cluster, then port to a place where you deny LoS to everything to force it to close to melee range. This concentrates stuff safely and effectively.