Why do buildings not use fireman's poles already?
I think you'll find that fire stairs are the best solution available today. You could augment them slightly, but there's not likely to be a revolutionary change to re-solve the problem of evacuating a building. Saving lives is serious business. It stands to reason that very smart people have thought long and hard about this already.
1. Put 'parking areas' every few floors for the slow or injured to wait while the crowds pass.
We had a fire drill the other day. There are 33 stories in our building and normally I can make it down in under 5 minutes. However, the stairwells are only made to accommodate two people side by side. There was a severely obese man in front of me and this obese person had to use both feet on each step. As a result, it took 9 minutes to exit the building.
Doing some back-of-envelope calculations based on the numbers in the above example, it takes just over nine seconds(9.09s) for an able-bodied person to travel down one floor. It takes over sixteen seconds(16.36s) for a handicapped person. If you were to put space every fifth floor, the worst-case scenario is adding ~37 seconds of total travel time for the people stuck behind the fatty.
But this useful in situations where you experience a new injury in the stairwell.
Evacuation policy for the places I've been at (I've been stiffed with the responsibility of fire warden, so speaking from experience) is usually for people that are infirm or incapable of travelling down a fire escape is to have them wait next to the fire doors - in the common areas, not within the stairwell.
Instructions are to send them down last, or if they refuse to go, leave them there and let the authorities know there's people still within the building.
[EDIT: adding this paragraph] A fire door is a pretty high-tech piece of equipment in itself. A good door is able to withstand a raging fire for over an hour, while keeping a person on the other side of the door unharmed. During a fire; people do into the stairwell, they don't necessarily need to go down the stairs.
2. More fire escapes.
To prevent tripping injuries, people need three points of contact: two feet, and one arm. The arm being satisfied with a hand railing.
This means the width of a stairwell is rather precise - designed so that people can travel two-at-a-time, but not three-at-a-time. You could make a four-wide stair, and add a hand railing in the middle. But the consequence of this is that that 'outer' stairs are about* four times larger than the 'inner' ones. Four times larger, means four times the distance to walk, and four times longer to exit.
TLDR: You can't make fire escapes bigger.
Instead, simply put more fire exits in.
*assuming the inner stairs are 600mm wide, around a 600mm cavity in the middle.