I have also used the following for vertical elasticity: 

• Efficiency: the ratio of utilised capacity to allocated capacity
• Variability: amount of variability in performance/QoS metric e.g. throughput or response time derived using control theoretic measures such as Integral of Absolute Error
• Adaptation: (which you have listed), you could also break it done into time to adaptation after a scale up or after a scale up

Thank you, Dr. Ilbidunmoye,

I think efficiency (= (4) Resource Utilization) has been listed. 

Can you explain Variability?

Fault tolerant is another performance metric.

We collected all metrics

in this article:

Article Performance Evaluation Metrics for Cloud, Fog and Edge Compu...