The current codex is not the best iteration we have ever had. However, Sixth Edition Warhammer 40,000 brought some good changes for Tyranids.
Our army is not one that can simply rush across the board with a random selection of broods and a winning smile. Playing Tyranids requires a plan along with the tools to execute it. The models are characterful and overall it is a fun army to play.
I hope Bonzai doesn't mind me quoting him, as I believe he sums up the current state of play.
Synergy is possibly one of our most important tools. Setting up beneficial interactions between our broods reaps great benefits. There are a couple of ways this can be achieved: Psychic Powers, Special Rules or Abilites and the way that Broods interact on the table top.
Tyranids have some strong psykers and much of our synergy can be provided by them. As many of our broods are either weak and numerous, or start off fairly tough the ability to buff them or debuff their targets has perhaps a stronger effect than on, say, Space Marines. Hive Tyrants and Tervigions get a couple of powers so have a higher chance of a useful one.
Commonly Hive Tyrants will swap their Codex powers for a roll on the Biomancy table. Even the 'poor' Biomancy abilites duplicate or improve upon the basic Hive Tyrant powers while those mentioned below provide signfiicant benefits.
In keeping with the ability to spawn and buff Termagants, Tervigons can also benefit from Biomancy powers - however, it is not uncommon to keep Catalyst.
Zoenthropes generally keep their Codex powers but some players enjoy swapping their powers out for Rulebook powers to create a support unit with a toolbox of powers.
As to why Biomancy powers are so popular, Iron Arm can make a Hive Tyrant or Tervigon much harder to kill while also increasing its offensive power.
Enfeeble is a fantatically synergystic debuff. Reducing an enemy unit's Toughness has three effects:
- Easier to wound - obvious but very important for S3 Gaunt and volume of fire shooting from Termagaunts.
- Toxin Sacs on those same S3 creatures may not get to re-roll fail wounds.
- Casting the power twice on the same unit can result in Instant Death from S4 attacks.
Special Rules and Abilites
Another avenue for synergy is the handing out of abilites such as Outflanking or the improvement of Reserve Rolls.
Tervigons have a very obvious Synergy with Termagants
Brood Interaction on the Tabletop.
This can take a number of forms.
Firstly, some of our creatures are fairly pathetic. Attacking an enemy with two broods improves the chances of a favourable outcome.
Creating a 'Human shield' with cheap broods like gaunts can be used to protect more valubale broods from assault and/or give them a cover save against shooting.
As our Monstrous Creatures lack Invulnerable Saves and some of our medium sized beasties such as Raveners and Warriors are very fragile they need protection if actual cover cannot be found.
Taking a round of Overwatch fire is also the lot of Gants or Gargoyles so that other, more deadly creatures can safely engage an enemy unit.