It depends on what you are trying to say...
Daniel is ALWAYS missing class.... it means he never comes to class... it �s a negative action always being repeated.
EG: He �s always swearing as opposed to he always swears.
      He �s always arriving late
      I �m always losing my car keys
	She �s always complaining
 (I would not say he always misses class in this case however I would say it to highlight the reason..... He always misses his math class in the morning due to heavy traffic) 
Daniel always has to miss class... it means there is a reason why he cannot come to class. 
He always has to miss class in the afternoons because he is going through medical treatment. 
Does that make sense?? :) 
Hope that helps x