In 7th edition, I still find that jungle swarms have their use, but as mentioned the use is very limited.
The one tactic that I have found to consistently work depends largely upon how the terrain is deployed. Assuming that there is a forest/ruins/etc. on a flank, I try to park 1 or 2 bases in this piece. That way, my opponents have much more trouble bringing their cavalry (light and heavy) through the corridor along the terrain piece as I can hit them in a flank as they pass. As I generally will only face one model/and the unit generally wont have a high CR, I can effectively tie the unit up. With a 60 pt base I can deny an enemy a large portion of a flank (assuming his flanking force isnt a 10 man Chosen Knights or Black Knights). Although not a glorious role, it is an option well worth taking.
Beyond that, there are really only 2 uses I can think of. One of those is redirecting charges more easily than with skinks, as 1 base makes it much easier to force the enemy unit to charge in a specific direction. This is really only worth it if your using a lone slann as far as I can tell, as terris could do the job well and get away most times. The second thing that ive thought of is as a suicide unit. Being unbreakable, one doesnt have to worry about fear/terror (although this usually isnt a concern anyhow. With 2 bases one should be able to direct 10 poisoned attacks against a mage hidden in a unit (a portent of far would be an easy way of making this better). Its a cheaper method than risking a JSoD, and a JSoD would be better served charging chariots/cav anyhow.
All of these tactics are rather inflexible, but thats just my 2 cents
