Yes, it is the triggers will eat/kill everything else in the tank the huma huma will get about 10 inches long and one day it will figure out that the other fish are made of meat. They are pretty chilled as far as triggers go but, I wouldn't add anything smaller than it is. The niger will eat any inverts you decide to add. That is also about the bottom limit for the tang and they are ich magnents when they get stressed out and the huma will do that sooner or later.
hth
p.s. I'm going to give you a break down on the size of your fish as adults not to try to push some mythical inch of fish to 5gallons rule but, to give you an idea of what you're in for.
huma huma around 10 inches 80 gallons
Niger 1 ft 100 gallons
Tang depends on which one you have the common yellow tang gets about 8 inches long
The tomato will get 4 1/2 or 5 inches long and they are pretty aggresive it might stand up to the huma .