I disagree with this statement so much I can't even express it. Lianas skill opens many options with units Like SA Mirabell or Momiji who have self paralisis. She helps with dracoliches, running mummies, vampire lords, chimeras and many more BS enemies. Her skill and awakening ability are great. And the cost issue? It can be migrated by having low cos backup healers like feng shuis.
I'd keep two even though it will be extremally annoying to get them both rainbowed up