The two popular crisis configurations seem to be
Fireknife - plasma rifle and missile pod
Deathrain - twinlinked missile pods
There are names for almost a dozen other suits and they will be mentioned in this thread no doubt, but these two are the most popular.
Crisis suits are still difficult to kill in 5th however TLOS means they are more likely to be targeted by heavy weaponry. Shield drones do offer good protection against this, or you could stick with hiding them behind (the limited available) LOS blocking terrain, jumping out, shooting, and jumping back. A Tau army without crisis suits will find it more difficult to kill as many tougher threats such as dreadnoughts and terminators.
While crisis suits are very important in a Tau army, they are relatively easy to use. Just remember in your movement phase the words "will they die if they go here?".
On the other hand, units such as pathfinders, kroot, stealthsuits, piranhas, and vespid require a lot more skill to use effectively.
The tactical uses of kroot include pushing back enemy infiltrators in deployment, and covering areas of the board to deny deep strike. For example, against drop pods, surround the hammerhead so the meltagun can't be within 6", and against lictors, spread them out over a piece of terrain so your suits around that piece are safe. They can also deny areas of the board against outflankers by lining up the short edge, preventing nasty assaults against anything other than your disposable unit of kroot.
The most common thing I do with my kroot is deny assaults against my suits. This is usually called the tactical speed bump. The idea is, the assault marines are within 18" of, say, your broadsides, however you stick a unit of kroot in front of them (the broadsides). You kill some of the assault marines with your firepower, however it is not necessary to kill all of them this turn. They charge the kroot, kill them, and consolidate. You now have a second turn, and they are now close range, making it easy to kill the whole unit so the broadsides can live for the whole game.
Kroot also make nice pill box units, stick them in cover and shoot, and when the enemy assaults them you kill a few more. Fire Warriors do this better, kroot have the options above.
Personally I put my fire warriors in devilfish. So my first question is the tactics involved with fire warriors outside devilfish. All I know is that calling them static is misleading.
Fire Warriors in devilfish are easy to use, I think. Wait for the enemy unit to be small enough that they can't kill the fire warriors back, then unload and shoot them. Keeping fire warriors in devilfish in reserve is a mixed blessing. There seems little point against a shooty army. However against an assault army you may be able to apply a lot of firepower to a weakened assault unit at your lines. On the other hand, they could come on the board and do nothing the whole game, missing the action. All I can say is I would definitely keep a fish squad in reserve in dawn of war against an assaulty army that deployed first.