The problem with spiders in their current state is that they are missing two important unit roles.

The first role is a territory capture unit.
Units like this tend to be reasonably fast and are able to establish the front line, units like this include, scorchers, halberds, pyros, glaives, and bandits. The problem is that when a player chooses spiders, even on a map with rough terrain it is difficult to establish a front line.

Another thing is that the spiders lack a cheap reliable riot unit.
The venom is fine if the opponent just sends two to four glaives. But when he does an all in glaive rush, this is where the venom fails. The venom can only stun it can't kill anything!

The solution to this problem is to allow the venom to do damage, not much but enough to kill light raiders quickly.

I think your analysis is strong, but in conclusion I actually think spider lab is the design that shines. You have a really interesting raider unit, the flea, which is only enough to kill naked expansion but can get you lots of hidden los over the map. You have an interesting riot unit that cannot kill anything on its own but is super-effective as support or when supported.

You have lots of units with strong strengths and weak weaknesses. Nothing is straight-forward, and you need to synergize your units well to maximize your effectiveness. For example, venoms and fleas together work well at fast attacking and territory control. Venoms and cudgel or recluse are better as a main-army composition. Because their strengths and weaknesses compliment each other, you can make interesting compositions.

If anything, it is more the other labs that are kind of broken and/or need work, because you can get so much effectiveness out of a single unit, because there is less synergy or need for synergy. (Bandit is probably the worst offender)

We've tried to make these factories more viable as start options, because more start viable factories is good and opens up more diversity from the start of the game. However, they make the map seem 'flat' and really make terrain sort of irrelevant. So if they are secondary factories most of the time, that is okay and may in fact be better for the game than if any even slightly hilly map is a spider-only map where the terrain doesn't matter (Already too much that way IMO).

The flea+venom combo requires a lot of micro to pull of (like so badass micro, that you should really try using normal facs and get to top 5), since venoms like paralizing your fleas as well, but if you have godlike powers and can pull that off on a day-to-day basis, then spider fac becomes a viable starting fac regardless of terrain (since then you can counter raiders witout assults or skirmishers helping, which is the only major reason spiders are hard to do in a 1v1 as starting fac, all other resons you can usually live with).
The synergy, yes, is strong with this one, but most spiders are made by 3-year-olds and die to a sneeze, so no matter how you combine them, they still die really fast, this is why the counter to spiders (the whole fac) is raiders - they can get close quickly enough do shoot, can be massed enough to surround the venoms, can avoid a few volleys of the recluse and can kite the hermit for eternity. So effectivly, the spider ball can be destryed by using said bandits, glaives or scorchers (if there are no hills). I'm not taking the crabe into account, since it's an end-game unit, but even it is counterd by a few raiders because of the slow turn speed of the turret.

I'm sorry, Anarchid, but I'm supposing a game where you enemys have brains that are sometimes used. The crabe may have massive AOE but normal raiders don't hug it to get burned.
And the spider raider+riot combo works if you can keep the fleas at a safe distance form the massive emp-blast of the venom (which, as you said, requires you to be goddie). If only fleas had a little more range...

imo increasing fleas range would fix this issue, (lower dps to compensate)
it has been said a lot of times in forums though, so i guess there is a reason for not doing this.

quote: so i guess there is a reason for not doing this.

The reason is that venom should have chain lightning, which also has been mentioned and agreed with countless times.

Therein lies the problem that chain lightning requires a gadget to actually chain the lightning, and some way to display it, which, from a naive view, looks like, say, 150 SLOC. Flea range, on the other hand, requires 0.5 SLOC to implement.

4 recluses + 1 or 2 venoms. Obviously. Fleas should give you info about techswitch, so good luck with a surprise napalm...

Did i mention hills?

Don't forget, that spiders lack long (recluse is not long enough) range unit. Arty will drive a spider player mad.
Also the hills can work both ways, even if you'r not a spider player, but that's pro talk and i'm not allowed to speak about that.
If you can deal with the tarantulas, then air will rip any recluse ball in a matter of seconds. Then mop up the remaining venoms with anything you have left. Just a reminder, that recluse have about 600HP (double defender) and cost something like 300. Every kill puts you that much more foreward then him (where you can loose 3 bandits for a recluse and come out on top).

The only arty you REALLY want to use against spiders is Firewalker (which is THE counter). Also napalm missile. You can also just do attrition damage with snipers (if you can defend from fleas) or Penetrators, and a Tremor will also tear down any hills the recluses are on.

But investing heavily in arty requires you to have an entrenched position, often ceding territory, etc. A decent assault force will just roll over you.