Ok, well, first of all, I understand that the battle between God Serena and Gods of Ishgar was off-paneled, but we did see some feats from God Serena. After being hit by 4 attacks from each of the wizard saints, he still managed to hit and almost kill every one of them. Even Hyberion's attack, which is pretty OP in itself, had little effect on God Serena as the paralysis couldn't do much to him.
Second of all, if what the Gods of Ishgar did was hype, Laxus would be in the same category because his nuke was nullified by August's shield. August never said that Laxus' nuke would have killed Ajeel. That was the misconception from the fans. He did say it could have dealt quite some damage though; however, even though August is somewhat reliable, his statement could either have been false or overly exaggerated because Ajeel thought he may have been able to handle it.
Lastly, it is true that God Serena didn't show CQC skills, speed, etc. But the fact that he beat all 4 wizard saints must mean he is at least average, if not proficient in all of those stats. Just like August. What has he shown? Only defense from a shield and the rest was hype from Makarov. Although this is all we've seen, we can still rank him pretty high after seeing that he casually blocked Laxus' nuke. Similarly, God Serena was shown to use a variety of attacks and most of it was strong as it dealt damage to the 4 Gods of Ishgar. We have no proof whether Hyberion, Wolfheim, and Warrod are durable or not, but we know Jura is to a certain extent. We also know that the rest are above him, so logically, it makes sense.