That's not even remotely true. Energy Blast is off of the GCD so it is, quite literally, free DPS. Gut is on the GCD so, if you're actually comparing worst cast, it's Gut v. Hammer Shot + Energy Blast for combined damage. Energy Blast + Hammer Shot actually deal *more* damage than Gut, and that's completely ignoring 2 major aspects of it: Gut is a Dot, so it's *delayed* damage rather than up front damage (delayed damage is worse for a tank because you want threat right away) and Gut ends up costing 3 more Ammo than Hammer Shot + EB (since EB returns 1 ammo and Gust costs 2).
You know . . . on paper it does do more damage, when I load into swtor this is what I see:
Energy Blast does 786-803 elemental damage with a 15 second cooldown, it's instant cast.
Gut does 695-759 up front, and then 877 internal over 15 seconds, no cooldown, instant cast as well.
The total damage from Gut over the 15 second period is over 1k. Though I finally understand what you're getting at, because EB is off the global cooldown you can use it inbetween or in conjunction with some other ability like hammer shot or something else. Where as Gut doesn't have that luxury and if you add in the extra damage from whatever secondary ability you use overall Energy Blast should be getting you more damage in practice especially when you factor in the +1 ammo it gives you.
side note: Though I've come to the conclusion that EB comes at the cost of 6 second cd interrupt . . . I think that's why I didn't like it at first. I guess I'll have to give it a try. Thank you Kitru.