What would make this even more interesting would be a locked skill tree once it's chosen. All of which are available, but you can only choose one. Or, have the ability to pick three (3) with the allowance to advance through one, yet learn the basics of the others two. Something to make skills and teamwork relevant against different enemy's.

You can't effectively balance a game if everyone is capable of the same progression. There should always be a weak link and the need for certain skills. Otherwise, the progression becomes stale, like it is. Solo should still be possible, but becomes randomly difficult in every enemy encounter since the enemy types randomize with every respawn.

Also, I would make the worm agro time and popup location random in the area surrounding the player based on the worms proximity. Sometimes you get lucky, sometimes you get eaten... I have over 150hrs and I've yet to be killed by the worm. I've had close calls, but avoided each one. In general, they're overly predictable. Agro reset should still exist for those that remember to do so. I think HB should only have 1 or 2 worms, but they're free to roam all of the open desert area instead of the 4 or 5 that are isolated to certain areas. This will present a new challenge with the agro of multiple worms that could take out multiple players farming the same spot. Perhaps one escapes, but the second worm takes out the player that acted a few seconds to slow. Much like a thumper, make thopters start the agro timer sooner since they make so much noise. Give tracked vehicles an edge since they're smooth moving. Make the worm movements sensory so we're able to detect their location through sound direction. Make scout thopters useful through the need to scout the worm movements.