I find it annoying how easy it is to kill high level neutral heroes. This mechanic means that these awesome heroes tend to never actually get used in the game because it's very easy to kill them before anyone can get the tech needed to recruit them. It also means that some really awesome loot is available too easily. One option would be to simply make them unkillable but I kinda like the option to possibly kill them but I think a better solution would be to give them some support. This is just some idea off the top of my head.
Level 1 : No support you have to rush to find these guys
Level 2: Small army. Exploration tech isn't too hard. You need to hurry if you want to get them though.
Level 3: Medium army + Guardian Statue. These guys should last a while.
Level 4: Medium Large army + Guardian Statue + All unit buff cast at battle start. These guys need to last well into mid game for getting the level 4 tech as literacy is a prereq.
Level 5: Huge army + Guradian Statue + All unit buff at battle start + Damage spell cast on you every turn. You generally don't want to mess with these guys. They have a real following and they should be sticking around well into the late game.
