What you are doing now before your dance practise is absolutely fine. Every person is at a different level of strength and you must tailor it to fit your needs.
A warm-up and activation for one person might be enough to build strength in another person.
Do strength separately on other days. Choose one warm-up, one strength routine followed by a flexibility routine first. If that is easy, try to do two strength routines one after another.
Do these two to three times a week for maximum benefit.
Take a break between strength and dance days if you feel too sore to dance.
Hope this answers your question