My tyranids won a game against Elysians with Valhallan allies somehow. Game ending after turn 5 so I didn't have to watch his flyers wipe out my army while I couldn't hurt them probably helped.

Basically my 1/4 strength genestealers and 1/2 strength termagant squads were enough to beat him once I was close enough.

Choosing biomancy on two broodlords and only getting ranged powers was pretty useless. As was telepathy once I worked out Broodlords can't actually cast invisibility.