Are tyranids good in 8th edition?

Tyranids have a lot of good toughness, decent save, high wound models, as well as lots of cheap, average toughness, low save models – not unexpectedly. Some units such as my beloved Carnifex are pretty cheap for their survivability, whilst others such as Trygons seem relatively fragile for their points cost.

Are Tyranid Warriors any good?

Warriors are great with a reroll to 1, especially if you bring the Prime. Jormungandr is also a good choice for a 3+ armor save at range, so they can walk up the field, lay down fire, and be a bit more resilient to it back.

Are tyranids competitive?

Tyranids on face value probably sit in the upper mid-tier, especially after some minor buffs through the Blood of Baal. They aren't Space Marines, but they have a broad range of options that can all be competitive.

Why do tyranids have guns?

Subject: why do tyranids carry their weapons? They carry weapons because it looks cool. The rest of them is complete bunk.