Lysander and Vulkan are not "broken", just very tough to fight against.
Lysander has the same stat line as Calgar, except his wargear is a little different. He always strikes at Str 10 and Init 1, and if he attacks a vehicle, he adds 1 to the Vehicle Damage chart (like an AP 1 weapon). He comes in Terminator Armor and has a Storm Shield. Combine that with Eternal Warrior, and you've got a tough IC to kill. Lastly, he replaces Combat Tactics with the Stubborn ability, and any unit that he is attached to can reroll failed to hit rolls with Heavy Bolters, Bolters, Storm Bolters, and Bolt Pistols. Oh, and he also has Bolster Defenses, like a Techmarine gets.
Tough, yes. Broken, no.
Vulkan is a little less intimidating. He comes with Artificer Armor, and also has a 3+ invulnerable save, but doesn't have Eternal Warrior. He has a mastercrafted Relic Blade, with an attached Heavy Flamer. He replaces Combat Tactics with giving your entire army Twin-linked Flamers, Heavy Flamers, Meltaguns, and Multi-meltas, and also makes all Thunder Hammers mastercrafted.
Great choices for any list, and individually hard to kill, but I wouldn't go as far as to say they're broken.