T8 Tanking

[Marukoban]

Hi, I'm using Paladin @i104 now. Solo tank T8.
I noticed the boss can hit very hard, especially if it crits.
Need advice from experienced player here.
Should I save my buff for landmine and dreadnought, or should I also use it in between landmine and dreadnought?
For now, I save the buff for dreadnought and when RNG grants me 2-3 landmine on South side. Sometimes I got real close to dying in between and thinking whether I can actually utilize my buffs better.

Also looking for advice on spacing buffs for T9
Do I just save them all for Ravensbeak, Heaven's Fall and Bahamut's Claw?