I believe runetap is one of the main strengths of the blood spec. It can save your life if a healer is impaled or silenced, and will almost give you 50% of you health back when using it while vampiric blood is active.
Many people still forget the great Deathpact, it performs like an extra cooldown to give you 40% health in a high damage phase of a boss fight. The only downside is the ghoul's survival for the next 20 seconds that you need to sacrifice him.
About your statement on stacking stamina, in today's World of Warcraft a tank's worth is based on the number that shows on his health bar. You wouldn't believe how many people refuse a tank with low health but can master his class and perfect his skills.
2.) What is helpful.
And that's also what is "fun" about the game, exactly like you said.