I know this is a really old thread at this point, but I feel like your "expertise" is spreading misinformation that needs to be corrected. Corsair may not be the Lost Spirit Ship, but it has its uses.
1) It's a third-tier flying unit which shoots air and ground independently, and the ground attack knocks small and medium units around with a decent splash radius.
2) It lets you summon Banditos on demand, 4 per ship, for 30 power each. Banditos who, I may add, get a 50% damage increase for every 3 friendly units nearby (including each other), up to 150%. That's roughly 1650 attack power, higher damage than fully upgraded frenzied nightcrawlers, as long as you have enough units to not see individual portraits.
2) The corsair gives off an aura increasing all friendly human units' damage by up to 50%. You know who counts as human? Banditos, Forsaken, Nomads, Bandit Lancers, Firedancers, and Rifle Cultists to name a few. This damage buff combines with other damage buffs; Banditos, for instance, get the 50% on that 1650 effective attack power, raising their attack to nearly 2500. It was already better than frenzied nightcrawlers; now it's better than Mutating Frenzies with 1 level of Deathwish. But it's even more interesting on units with special abilities, because it also affects those: red nomads can deal over 1000 damage with sky scare if a corsair is nearby.
But as I said, Corsair is not Lost Spirit Ship. It isn't your end game. It's a support unit. It and the human units it buffs are relying on strong tanks who won't get pushed around by bosses and towers: units like Soulhunter and Bloodhorn. Bloodhorn is ideal as it's both an anti-XL card and an anti-building card with stampede, so you can send one to bulldoze key structures while others tank the big bads, and banditos can clean up the small stuff.
To be honest, I do have a few problems with the corsair, but I consider them bugs more than anything. They have a hard time finding space to drop units, because they try to drop all units in a large cluster directly underneath, rather than just putting them wherever they can like other summoners. And ... I know this might rapidly become too OP, but they are the only summoning card I know of to abide by unit limits. While most of them summon timed-life units, Satanael and Sunken Temple both summon permanent forces, and both ignore the limit. So if the team ever finds time to balance cards, I'd like to see some consistency here.
As for your generic statement that t2 is not strong for bandits, I'm not sure I can even see where you're coming from with this statement. Bandits in T2 can use Fire Stalker for siege and choose between: Windhunter, Shadow Phoenix, and Skyfire Drake for air power; Spearmen, Banditos, Nightcrawlers, or Rageclaws for infantry; Nightcrawlers, Scythe Fiends, or Stalkers for speed; and Sorceress, Commandos, Gladiatrix, or Darkelf Assassins for archers; and for defense, Rioter's Retreat + Commandos or Time Vortex + Sorceress are nearly strong enough for T4. All in all, bandits combine all the aggression of fire and shadow decks with an insanely good t2 defense, and a lot of bandit cards/strategies work as well in splash decks as themed ones.