Well yeah you could plan around them to a degree, just like you plan around demolishers, vultures, cops, regular zombies etc. But it would add an interesting and dangerous element to base designs and horde nights, and you'd have an extra resource tax for spikes, and have the risk of the zombies taking out your spikes etc. They could also make webs coat spikes too and make them safer to climb over
ATM spider zombie is by far the least unique special zombie and is only annoying because it's mildly harder to hit. The web idea would be pretty neat and create very memorable horde nights where you were standing on a roof shooting away at zombies when suddenly they started swarming up one side or got to an upper floor you weren't expecting them to get to etc