So from my understanding you can use telepathic summons from a slann/kroak then have them teleport onto the troglodon via arcane vassal right
Yep. They can teleport to any skink wizard within 12" of the Slann caster, or to the Troglodon anywhere on the board. They have to be wholly within 9" of the Slann or skink vassal, but if there's an Astrolith Bearer in range of the Slann, then they can be summoned wholly within 15".
You can also use Telepathic Summons to teleport Saurus to the other end of an Umbral Spellportal (endless spell) for crazy range. Cast the Spellportal up to 18" from the Slann (24" with an Astrolith Bearer), and then use Telepathic Summons to bring the Saurus within 12" of the Spellportal (18" with the Astrolith Bearer). NOTE: The update to Umbral Spellportal with the General's Handbook that comes out this Saturday makes it difficult to cast the Spellportal through a vassal, because now one end of the Spellportal must be within 1" of the caster. If we measure the spell from the vassal instead of the Slann then the near end of the portal will be by the skink and not the Slann, so only the skink can use it. That reduces the range of this trick a bit.
The FAQ (rumored to be coming out this Thursday) may change this, but for now they can teleport and still move, or teleport right into combat.
If you cast Heavenly Frenzy on the Saurus Warriors, they can teleport to the Slann, skink vassal or Spell Portal and then run with their +1 to run rolls (or use At The Double for the 6" run) and then charge with their +1 to charge rolls, to get them a good distance (18" on average) from their teleportation location.
If we combine all that for maximum range, it's overkill. Imagine the common scenario in which we have a Slann, a Skink Starseer just inside 12" further up the field from the Slann, and an Astrolith Bearer boosting their ranges and spell rolls. The Slann casts Celestial Equilibrium to give other casters +1 to cast. Then the skink casts Heavenly Frenzy at +2 to cast and 24" range on a unit of 20 Saurus Warriors. Maybe we add Mystic Shield and Empowered Celestite to the warriors as well. Then we cast Umbral Spellportal from the Slann, 24" up the battlefield, and use Telepathic Summons to set up the Saurus Warriors wholly within 15" of the distant Spellportal, 39" from the Slann. Then the Saurus Warriors run 7" to 12" (9.5" average, or use At The Double to guarantee 11") in the movement phase and charge 3" to 13" (8" average) in the charge phase. So together, you were able to get the Saurus Warriors into combat 49" to 64" from the Slann (56.5" on average). That's basically the entire battlefield on a 44" x 60" table. That could be limited a bit by terrain, but you can also use the Slann's Gift of the Heavens command ability on the Saurus Warriors to make them fly over terrain, and also be -1 to hit vs missile weapons to prevent losses from an Unleash Hell when they charge.
At least for now, it's a very flexible spell with some killer combos.