The following post is assuming you mean trance - empath has no effect on non-combat units, since they can't attack.
Formers - I know a lot of people typically use trance formers (and the various puns that go with it ) but I tend not to. Or rather, if I do, I will also equip them with armor.
Basically, the non-combat bonus will nullify the +50% bonus. Thus, the unit will defend at normal strengt for any unit - not favourable odds, in any case. However, it might be worth (if you have the energy) upgrading them to 0-2t-1, as any unit with armor will not get the non-combat penalty, and as such will survive the vast majority of mw attacks. The downside to this, of course, is that it is rather expensive, and is only worth doing if you build a bog-standard former, and then upgrade.
On crawlers - I know a lot of experienced players heavily advocate this, as it can be useful in many ways -
1) It helps defend from psi units (when combined with armor, of course).
2) You can cash the crawler in for its full mineral value which will be a lot higher than it was originally.
I tend not to use this as much as I should, but it can be an extremely potent weapon if utilised properly.
Rovers/ships, pod popping, it is absolutely 100% worth it. Any help killing/defending against mws is a massive boost. When combined with armor, it is also worth it on transports - mainly because the cost of losing 8 land units to an IoD can be massive.