OK. Are you able to provide specific details on how they are good?
Not my question, but:
-Drill Rangers I can't see any good use for. Marines are better in every situation I can think of for a light unit even if only attacking one target, because they don't take retaliation. Better against ranged and artillery I guess? The two units strong against light units...
-Shredders have low range, but they have enough movement to reach just about anything that's capable of attacking them except for artillery. Low movement costs makes them surprisingly mobile. Compare to the Champion, which has a higher movement score on paper but gets tripped up by basically every type of terrain that isn't plains. Low range ultimately just makes them bad against artillery, which is a heavy unit's weakness anyway so arguing about that is going to ring pretty hollow.
-Nail Storms are pretty widely agreed to be the best unit of the five. Their one big drawback for me is that they're very annoying to move. Battlefield terrain is not very kind to them, especially when it comes to landing on rubble to activate their stealth bonus. Perhaps a moot point though, since stealth only really protects them from other Nail Storms. But I have noticed that the battlefield tends to favor defenders in this regard, placing far more rubble tiles on the right side of the field compared to the left. Bit of a tangent here, but I'm wondering if maybe the stealth was given to these units to make it more annoying for players to face, moreso than a benefit for players to make use of.
-B.E.L.T. is a better Sniperbot, but I don't think that's the comparison people care about. The Rocket Troop is still faster, though by now its other stats aren't looking too hot. I think this comparison is definitely pretty up in the air though. Players with lower boost will generally get better results from using the B.E.L.T. compared to the Rockets, though with such low attack ranges even players with stronger boost can make good use of them against the SAAB units and they'll even two-shot Nail Storms pretty easily.
-Offensively, the Hover Hammer feels a lot like the Drill Ranger. Don't see much use for it compared to the Sentinel. However, I can see uses for the Hammer on defense. It's faster than anything you're going to be attacking with, so it can get its terrain bonus before you hit it. Not a big bonus, but it's something. It also tends to hang back with units that have low movement (artillery), which is important to keep in mind when using Rogues; if these Rogues can't move into the Hammer's attack range on their turn, the Hammer's going to charge forward and hit a normal/transformed unit instead. Which is usually bad for it because of retaliation, but it's also bad for you because any damage a player takes is generally bad, which is why you're using Rogues in the first place. I've found that this is the reason why 1 Sentinel+7 Rogues almost always takes some damage against the 4 fast+4 artillery combo in GBG now that I'm in SAAB, compared to the same combo in SAM where I usually took no damage even at high attrition levels. The Hammers aren't reaching my Rogues because the AI's keeping them back with the B.E.L.T.s, and they're hitting my (transformed) Sentinels instead.
One other situation I want to point out here. When using Rogues in battle against Nail Storms, you have to be really careful. A Nail Storm placed in the top spot on a defending army has a pretty good chance of not being able to reach anything on its first turn except for the unit directly across from it. This is always the non-Rogue unit in the common 1+7 Rogue combo. If it's something slower than a Nail Storm, you run the risk of having it get Keen Eyed before it can move and we all know what happens next if the rest of your army is Rogues. But this also means that even if you're using Sentinels, that Sentinel has to stay out of range on its first turn or the same risk still applies. At least with the Sentinel though you can check to see if that Nail Storm is able to hit anything else before you decide what to do with it. Definitely worth pointing out (along with the Hover Hammer above) to support Agent mentioning that SAAB units don't pair as nicely with Rogues.
Summary: Nail Storms are the overall best unit, with the B.E.L.T. and Shredder being usable as well. All of the units have use defensively except for the Drill Ranger (the Drill Ranger just seems awful to me), which is perhaps what they were mostly designed for. The biggest takeaway from SAAB for me is that this age wants to be mean to Rogues, with one unit being able to semi-ignore them without needing to change the AI, and another making you roll the dice if you go into battle against them with 7 Rogues. I initially scoffed at the stat boost the units got after release on beta, but I think that may have had more impact than I realized as well. The handful of players with a huge attack bonus won't feel it as much which may have contributed to it feeling like nothing was really changed with them.