In 2.6 fire is now causing bleeding yes. And it can very well result in some sheevar doing nothing instead of killing a unit of yours, because it got its movement costs increased, leaving less points than planned. And they really have a strong urge to move through fire if it is useful for reaching an attack position. So, fire fields are a very useful weapon against sheevar and unarmored taman. It can also happen an already wounded sheevar moves through 6 fire fields and still makes a kill though. And civilians may also move through fire and will instantly die, so take care that none are between aliens and fire.
That map is "Old mine", a mean one where I loose almost all civilians most of the time. My strategy on such maps usually is to rush with lots of cannon fodder. Soldiers which are not very valuable, have little experience and which can very well be replaced, from a campaign point of view. On that map it doesn't work well most of the time since even with the speed boost the rush is too slow. Note that crashed UFO missions can be safely ignored without affecting nation happiness. An old mine mission with likely 12 aliens can only result in nation happiness loss so ignoring it may be better.