Out of Draheera, Anibal, and Methane, I always considered Methane to be the weakest 4*. So whenever I built a mono-GHEIST, I didn't use him. Now that Draheera is gone, he is the replacement until a better 4* comes along. He isn't that bad, it just feels that his 7 power is a little on the weak side. My 5* choice was always Wardom, so I didn't care about Methanes additional damage much. Draheera/Anibal/Wardom still posed a 2HKO-threat, which is all you ever needed. It was just a matter of higher power to get the damage through.
Mono-GHEIST took a big hit when Arkn joined Toro and Rolph on the side-lines, but even then mono-GHEIST was doing just fine because Platinum isn't a liability. Now with Draheera gone as well, mono-GHEIST isn't as scary anymore, although you can now use Mok in Platinums place next to Elke and Z3r0 D34d.
Those 4 damage 2* really help keep mono-GHEIST alive because of the potential they have in combination with Wardom.
And yes, mono-Skeelz did receive ridiculous buffs as of late with Dr Falkenstein and before that with Michael. You can now have 2 cards with 7 power who have a base attack of 23 in combination with a 10/7, a 10/4, and an 8/4 -2 opp power. This insane power and attack manipulation is the reason why Greem is such a viable choice for a 4*. Of course there is the big threat of potential 12 damage as well. But with 7 power and no bonus she is rather easy to defend most of the time. Skeelz big downside is the third 2* slot.