Lesiones are monsters that have some very attractive techs. Between submerge, showtime, tsunami, you have 3 techs that can do some major damage and have pretty good accuracy. The key here though, as with all monsters, is guts regain. While 90 guts regain isn't as slow as molasses, it definitely cannot recover the loss of 50 guts so fast. I don't really see much of a possibility for only int based Lesiones, but pow and pow+int based ones will do fine.
Tail Whip: Tail Whip is a solid rational/BLS tech. At 23 guts, you get a relatively accurate (50) tech that does 27 damage when maxed. This is a tech reminiscent of the heavily praised Remote Punch (see Henger guide), with the extra 2 guts cost made up for by the faster guts regain. Little techs like Tail Whip allow for monsters to recover from a massive guts lost; either by the enemy's tech or if the monster misses one of its own more exspensive techs.
Tsunami: Speaking of exspensive techs, Tsunami costs 50 guts but is Lesione's strongest attack at 57 damage and a respectable 50 accuracy. This is a vacuum tech that can be risky due to Lesione's slower guts regain. But it is the only Lesione tech that really hits the upper tier of damage, and for this reason, I don't think it can be ignored. At the Lesione Mayor's Cup though, I found it to be more of a big splash than a big wave for my own Lesione. Then again, i'm sure Torey found it to be the exact opposite.
Submerge: The tech that makes Lesiones something to be feared. Submerge doesn't do gutsdown, it doesn't do critical, it does damage. Cheap (36 guts), high (42 damage), and accurate (55 accuracy) damage. Its worth every minute you spend getting that jade orb for it. It is irrational not to use this tech, so I guess it can be considered rational.
Alternatives-
Lesihorne: A tech that doesn't seem impressive at first simply because it doesn't do enough damage (12) for 20 guts. However, against slower regaining monsters (lesiones, hengers, etc), the gutsdown (28) and formidable accuracy (54) can stop a monster from pulling off more exspensive techs while leaving enough guts on your lesione to pull off a submerge or tail whip. I'd classify it as a risk tech still though, because against a faster regaining monster or one with a BLS techs, it won't be as effective.
Showtime: A vacuum high risk tech. Decent damage (40), high cost (47), decent accuracy (48), and massive gutsdown (50). Its going to be good if your opponent has saved up all those guts, but otherwise, you'd be better off with a submerge, as its cheaper and more damaging. Recommended because its always frustrating when Lahas hits you with it.