Lurkers were far too powerful of a defense for zerg in sc1. Without siege tanks or air units (given the lurkers werent around AA and they usually were) you couldnt get thru a ball of 8 or so without losing half your army.
However if lurkers were a silent, single-target attacker that would be different. No audible sound other than your guys dying or your alarm going WE ARE UNDER ATTACK! and a slight spiking graphic.
As for the air issue. GIVE US OUR DAMN SCOURGE BACK! Theyre in the campaign, GIVE THEM TO US! Even if it removes Corruptors fine by me i hate those things. Scourge were required in SC1 because they could take out just about any air in big enough numbers or with proper timing.
EDIT: And it would be nice if Banelines did no bonus damage to anything, just a large chunk to whatever the heck they hit. I mean cmon its a big acidic kaboom. Even the mighty Thor would have some of the acid hit some pretty important gears.
Take that back, keep the bonus to buildings lol we need that.
Banelings do +20 damage to light units on top of the 20 SPLASH damage they are already doing.
But yes, I do agree that a New or Morphed Tier 2 unit is needed and which is what the second expansion is for. The unit that seems to be missing is the transition between tier 1 and tier 3. Idra has already pointed out that it seems the Zerg do not have a great counter against Terran Tier 2 mech.
Tell me what Tier 2 Zerg units that can directly counter Seige Tanks and Thors in the middle of a MMM bioball? You say Infestors? Neural Parasite is very situational and can be difficult to pull off. It's more likely that you'll be using fungal growth to kill the Tier 1 units, and then handle the Tier 2. There isn't a direct counter. You cant send in mutas to muta bomb 5 or 6 tanks in the middle of a bioball/Thor Combo. It get's eaten.
As for Tier 3, it's obviously different with Broodlords. We're not talking about late game. We're talking about mid game problems. A Tier 1 and Tier 2 combo for zerg is lings, banelings, Roaches, Hydras, Mutas and Infestors. There needs to be some meat in between for a Tier 2.5 which is why we're talking about lurkers or some other Zerg morph.
It's the same problem over and over on the forums. While I disagree that it's entirely OP, but there is a distinct advantage in a Tier1 and Tier 2 combo when it comes to Terran. Tier 1 and 2 combined looks like Marine, Marauder, Medivac, Ghost, Reaper, Hellion, Seige Tanks, Banshee, Viking and Ravens (with Thor being the next one up to tip the scale). How many Combos, drops and uses can you do? There are so many options.
Not ranting, just stating the facts.