I'm a low skill player (TS 7) and I've found HBDevs to be really underwhelming in a 1v1 situation. I can't comment on other setup teams, but those might need the same attention as HBDevs do.
I think the issues with them are the following and one combination of these suggestions should be implemented to make HBDevs a more reliable choice in Tier 1:
1. They cost a bit too much. I already suffer against double Slugga and double Shee builds. Maybe it has something to do with me getting power too early, but I think that SM need power ASAP to not get outteched. They need Flamers for power denial and Scout Shotguns against melee blobs. Also, HBDevs are a supposed counter to mass melee units, but I can't get enough of them out or can't get one out fast enough to make a difference.
If they would be cheaper, SM players could afford one squad while still getting some offensive power on their units.
Suggestions: Reduce their cost from 250 req 30 pow to 230 req 20 pow. Increase the pow cost of Vengeance Rounds from 10 pow to 15 pow to make it fair.
2. Their range is not long enough, or they're not effective enough at long range. Without a doubt HBDevs are a defensive unit. Their set-up and tear-down times, as well as their limited fire-arc suggest that. But for defending and area they're not effective enough. There are too much counters to them, and all of those counters totally take them out of a fight, usually forcing them to retreat. If you camp them at a VP or a Gen farm in a way so that they can't be flanked so easily (only from one way), they won't have enough range to cover the resource point from being captured by ranged units. They'll happily cap the VP or destroy your gens, while your HBDevs will only be able to tickle them.
Suggestions: Increase their damage at their max range, or even better, increase their range by 5-10 units (or more if needed). This way the opponent will be forced to actually disrupt or flank them instead of using cheap workarounds.
3. They do not do enough damage to be fearful. It's already a task in itself to find a good position for them, and once they start shooting, the opponent usually walks out of their arc, throws a grenade to disrupt them while being suppressed or actually reaches them and decimates the whole squad in melee. Once it occured to me that 3 full, upgraded Banshee squads charged my HBDevs head on, and without any problem reached my marines, tied them up, forced a retreat, and kill them while they were slugging back to base. The point of this unit should be that it can only cover a relatively small area, but it murders infantry in that area. Currently, they don't do that fast enough. Even if they do, the opponent can simply retreat from the middle of their field of fire at mid-range, gaining full speed fast, and running away with almost no losses. How's that fair?
Suggestions: Make them do 30% more damage mid-range. Should be enough to punish those who charge in, but not the ones who notice your squad and find a way around. Or make it so that HBDevs deal 20% more damage to retreating units, preventing cheap hit-and-run attacks from happening. Furthermore, increase the damage of Vengeance Rounds to vehicles, allowing SMs to counter walkers more easily without a Missile Launcer. With the ML it's almost too easy, without it, it's pretty much impossible.
4. For their current cost, they are too suspectible to ranged fire. It's somewhat okay if melee units butcher them, but there were occasions which on HBDevs were killed by ranged units, focus firing them down at a frightening rate. Shouldn't they be stronger at range than regular ranged units, since they have a mobility disadvantage?
Suggestions: Increase their HPs by 50-100. This will allow them to take more ranged hits, but melee will still be a threat. Shuriken Plats received a HPs buff, too, HBDevs should get some of that love.
5. They're far too defensive oriented, yet, they don't fill that role very well (see above points).
Suggestions: Alternatively, they could be made into a more mobile, offensive unit. Remove their tear-down time. This would somewhat be enough, so if this is done, the other suggested changes could be ignored. This way they still could be locked into melee, especially after being disrupted, but you wouldn't lose a squad to retreating after some melee units have reached your guys, despite them being fired upon by your Devs.
While thinking about changes one should also consider that this unit, along with other suppression units, is bugged. Sometimes they won't fire at all, other times they only fire at one squad while 2 or more charges them or they re-set-up if you order them to manually target a unit, regardless of those being in the firing-arc or not.
Personally, I'd choose the changes #1, #2 and #3. How about you? Do you think they need some extra power to become an asset instead of a liability?