Piccolo's power has increased a great deal throughout the Dragon Ball Super is less defined than characters like Goku, Vegeta, Gohan, and Frieza.
In the Saiyan Saga, Piccolo was the second strongest hero in the anime. He was the one who did most of the fighting against Buu Saga and most of Dragon Ball Super. However, Piccolo did get a few chances to show his power during the Universe 6 Saga and the Tournament of Power.
Piccolo's fights in Dragon Ball Super provide an idea of how powerful the Namekian has become. In the Universe 6 Saga, it's proven that - in a fair fight - Piccolo can beat Frost with his Special Beam Cannon, even if Frost is stronger than him. Considering the struggles that Goku goes through with Frost, it appears that Piccolo is more powerful than Goku's base form, but perhaps not any stronger than that.
Piccolo puts on an even greater display of his power in the lead-up to the Tournament of Power by scoring a victory over Cell at full power, which would imply that Piccolo may be able to beat Cell, one of Dragon Ball Z's most powerful villains.
How does Piccolo's power in Dragon Ball Super compare to the other heroes? Being able to beat a character capable of going Super Saiyan 2 is impressive, and serves as a good indication that Piccolo could easily defeat Goten and the young version of Trunks, who were never able to reach that level. Also, Piccolo remains above the weaker heroes such as Krillin, Master Roshi, but below characters like Goku, Vegeta, Frieza, and Android 17. How he would fare against Android 18, on the other hand, is up for debate. Regardless, Piccolo makes just enough gains in Dragon Ball Super to make him relevant if and when the franchise returns.