you could extend its jump in which case the unit might be passing, honestly Id increase jump to 12 and maybe give it more piercing... I dunno Im not a doctor... I do no that a unit that is only passing SHouldnt Be a Unit.
a unit doesnt neccessarily have to be cost effecient mind you, which is the other simply solution reduce its current cost to 20 and itd be a huge help something to offset the fact that it is indeed inferior to 2 warriors... maybe 25 would be fine...
but a unit doesnt have to be cost effective if it 'unique' if it performs a ROLE that is not performed by any other unit, or in that particular way, then it becomes valauble anyways, I dont think that Blaster Bugs are cost effecient but hey are USEFUL, because they fill the Longest Range aside from mega artillary, that the bugs have its unique and if you desire that role in your army youll pay the points. and generally some units cant be cost effecient because your army needs to have certain weaknesses, thats Macro-Balancing
SO if you made a Spider Cost effective with its current stats what role would it fill? the same one as a warrior, but weaker and slightly more mobile, it equals out it doesnt matter which you pick other than which you prefer... IF there is no difference between them... One shouldnt exist.
The major role I see the spider filling nicely, is short-medium range 'Disruption' something like what a Brain Bugs Ego War can get you, but not quite as good,
a Brain's Ego War is great, and has little risk initially as its 36 inch range... but you are risking that the brain will be caught in LOS and out in the open, and its a 300 point asset... the greatness is offset.
If say the spider had a ranged attack that was bad, did no Real Dammage, but prevented a squad from moving of any form until the unit Readies, or Prevents the NEXT reaction (but not all) or Spoils ready status, or any combination thereof, it would offer an alternative in a similar role, DISTRIBUTED Risk for a worse ability, and it would anchor the unit not as a main line replacement for a warrior, but as a support unit, something that disables an enemy unit to a degree, allowing warriors to move in, and this lets your brain be free for more important duties,
Or Hey dont like that? maybe the overseer fills that role too nicely?
Howabout we let the damn things be deployed with Ambush? 0-1 squad of them at PL3 or deployed like the enw independent snipers are, must be revealed by end of round 3, or lock them to say a terrain piece, but hidden... spiders strike me as a sneaky surprise unit and that would make having one big unit VERY viable. that would be new....
ok im done ranting...