all the more reason to share our collectives i have a rough 50/50 win/loss so far from the best but some things that may help.
heres a few i use.
early game i use 3 squad of hormagaunts and tyrant all naked/vanilla. ideal for chasing off smaller nodes or taking advantage of their speed(faster then typical units) to cap multiple nodes to once. best for 1v1 scenario as most opponents will try to collect all their units into one large kill squad making mobility our best actions. lot of micro managing and use of your mini map but not overly complex.
for 2v2/ 3v3 i most often use the same above or i will alternate and have 2 squad of hormagaunts, and 2 squad of termigants, pretty strait up hormagaunts are a screen unit for the termigants. when the lead unit of hormagaunts gets just under half health i retreat them (hit he X button) and let the rest advance. typically when doing this i try to keep a 3-2 termigant:hormagaunts ratio and only upgrade the termigants.
mid game: getting to teir2 units is important but try utilizing T1 as much first then worry about upgrades after, 3x warriors with barbed stranglers have bee reliable on every map, able to fire over walls, increased survivability for your screen units, and back to back shots will devastate multiple units on top of the suppression effects to.
a few venom warriors for their synapse upgrade to increase your ranged damage and all units health pools is great for more sturdy screen units and added damage form the stranglers.
alternatively if i have T3 open i get 4 units of genestealers and upgrade with rending claws, try to time the adrenal rush ability when your close to a key target (IE baneblade, landraider, titans) and pop it just as the majority get into melee range. their upgrade makes no difference what unit it is so they will rip it apart in seconds and if you can get a few warriors near by for their synapse buffs all the better with greater staying power.
a couple zoans are ideal, but i fear using them for the same reason i avoid tervigons on the tables. "SYNAPTIC BACKLASH" as powerful as they are once opponents see them their always focused hard and upon death (this is for any synapse) it causes a mass wave of damage and stuns all your own units heaven forbid you have multiples. >i had 10x zoans and the back lash wipe each other out in a domino style of knock backs and mass damage, so i advise only keep a few and space them away from the others.
carnifex i favor the strangle-thorn over the venom cannon upgrades but if you got the points take 1 of each, the bio plasma works just as good as the strangler for the splash damage. thorn back is great for breaking the lines or using charge to get away from the fight but most often it'll die before it does any significant damage.
swarmlord is a beautiful siege engine but personally im using him less and less. exception is when i go melee heavy and plenty of complimenting genestealers.
few side notes>
barbed strangler will hit rear armor on vehicles so it does less damage but compensated for with its splash and rear hits.
venom canons will only hit 1 out of 3 shots fired per unit. < this applys to hive tyrant, venom warriors, and carnifex upgrades.
tyranids can keep a large threat using only T1 units namely the strangle-thorn warriors were other armies almost always rush their T3s, this should give you a small window to steal some nodes or kill off a few units
when a unit retreats they take reduced ranged damaged but increased melee damage, so its ideal to have combinations of both
Game types consist of annihilation, and capture objective node.
most universal unit i find is strangle warriors (as mentioned above) rear armor on vehicles, splash damage, able to shoot over walls, suppression, and top it off their synapse adds durability (reduced damage received) to other units.
specializing units venom warriors in bulk can eat tanks from a far,
genestealers (when upgrade) will eat anything and everything in seconds with minimal risk,
canrifex larger versions of venom/barbed strangler with lot more durability, till it gets focus fired
zoanthropes longest ranged unit, increases healing of others in synapse range and a few of these using their focused ability can destroy anything.
hormagaunts ideal for bogging down units and if able try to set a few past your focus target so they can get a few more killing blows as enemy retreat.
termingants, when upgraded, can lay down a lot or fire power for very cheap so multiple units can often be wiped out long before they can get into melee range, but for warn even upgraded and synapse auras, they have virtually no armor and will die quickly to melee even against a should be weaker unit.
raveners are good for dealing with eldar wraith-gaurds and their zap cannon spam. just have them burrow and knock down the group while your main force is advancing, they are extremely fragile, so its best to pop up and then right away hit it the retreat key. they can put out a good rate of devour fire and decent in melee but their expensive and die to fast for my taste. how ever i have seen a large number of them clean through infantrys in shot time.
tyrantgaurd, afraid i have not found a great use for other then a expensive sacrificial unit. they can charge through blockades and go toe to toe with most dread naughts but they never live long enough to get past that initial charge, and as a fearless unit will not respond to retreat and often enough will divert into another enemy unit when trying to save it. bulky, fast and armored i have found taking 1 or 2 with a melee heavy build effective for letting hormagaunts and genestealers in the position they are needed
adrenal warriors, probably forgot to mention these guys above but that is because i often take only 1 for its diverse synapse ability, they are complimenting to hormagaunts and genestealers to further increase durability and they them selves become efficient tank/vehicle killers. biggest draw back is it requires T2 to upgrade with adrenals and most often can be better replaced with a zoanthrope, venom warrior, or even a tyrantgaurd. but in some cases (namely fighting IG myself) some opponents will put a couple of gun squads into a transport and taxi them around the field completely out of melee combat and most ranged combat to it can be useful to have a extra "can opener" (borrowed from our table top brothers/sisters) in case they taxied to close to another unit. their leap ability is also nice for knocking down gun lines letting more of your little ones into the fray.
im sure theirs a lot more and i just cant think of it at the moment but hope this will help ya some.
summery over all is utilize your T1 instead of rushing T3 especially when you consider most if not all out T3 units can be out done by a combination of our T1 and T2 and will never be able to withstand the other armies T3s, try to avoid spending resource on upgrades, same as the tables a handful of naked units can be more useful then risking 1 with a upgrade only to die off shortly after. And keep your finger over the retreat button and mouse hovering over the unit icons. best case is one unit gets wounded to about 1/3 remaining health retreat it and hope the others will be able to finish off the enemy unit. I myself will keep most my units on auto reinforce and as they repair return them into the fight just as the 2nd unit is ready to retreat, one steady flow of combat.
Such beautiful name with a dark secret. Welcome to the nightmare that is HIVE FLEET LAMIA!