Save yourself some salt. The Tyranid half of the Leviathan box is built to die to the Space Marines and win the game while doing it.

This is something I've been wrestling with since watching the battle reports and reading the datasheets for the units in the box. The Tyranid datasheets are flat-out weaker in a combat sense than the Space Marines. If it's not the Screamer Killer, then it's not killing the Terminators, and only the other single model units (Neurotyrant, Winged Prime, and Psychophage) can take wounds off the remaining marines efficiently.

What the Tyranid units can do is slow down the opponent and move more freely over the board. Rippers and Barbgaunts disrupt the opponent just enough to stop objectives from being taken/held for one turn. Termagaunts and Leapers have movement abilities to capture and steal some objectives for a turn.

The skill testing part of the army, is going to be stretching that disruption over 4-5 turns of gameplay. Keeping your ranged units at the edge of enemy range, and picking the right turns to charge the enemy so they won't score for a turn are the goals that the army is built for. Most Tyranid units won't survive longer than 2 turns, let alone the whole game.

The bottom line is that this Tyranid army is meant to die efficiently. When the indexes come out and we start looking at the rest of our faction's units that will likely change somewhat. But within the confines of this box set, the Tyranids are a low-power swarm army.

This opinion isn't meant as a criticism of the Tyranid part of the box, just an expectation setter. I often get frustrated by how fragile my units feel in 9th edition against similar units to what we're seeing here, and I'm trying to prepare myself for situations that will feel like a loss when according to the rules of the game (i.e the Victory Points) it was actually a win or a close match.