Stiger is fine, dont blob and you'll be ok
The sturmtiger is like the B4 precision strike except that it:
Cost fuel and less man power
Does not cost munitions to use
Doesn't require vet
Can't be countered by 2-click doctrines
Can't wipe stationary tanks way behind the front line
Is way better at wiping infantry squads at the front line
You missed out all (well alot of) the bad points let me help...
Is on a far less useful commander than the B4 (which also gets a heavy tank and 8cp and shocktroops).
It has 70% less range than the B4
It has a 1 min reload that immobilizes the tank (so a 2 click callin can actually kill/abandon it).
It comes at 3CP's later than the B4
Costs alot of fuel. (160)
Quite honestly its fine, after its first shot you should be aware of it and play more cautiously.