Yeah. Frieza's super doped power up in just 4 months is actually the least of the plot holes. At least they tried to cover it up with the saying Frieza had never trained in his lifetime and he was born with the power level he had during full power up on Nemak. Although it was conflicting with Frieza's own saying (in manga) of he was covered in dust during practice with his dad, but at least Frieza was indeed light years ahead of everyone else until Goku came along.
Future Trunks was able to kill Frieza within seconds. To achieve this kind of feat, Trunks was at least 50% stronger than Frieza if not more than double. And Android 17 took Trunks down with a single hit (it was said the future android was on the bar with Trunks, but the same Androids in this timeline somehow have double that power). Piccolo after fused with Kami was fighting evenly with Android 17. That was enough said... Piccolo right after fused with Kami could have made Frieza on Namek his pet since he had at least 3~4 times the power level of full powered Frieza. After his training in the time chamber, Piccolo got another large boost. Now all the sudden he couldn't even beat Frieza's soldier. (In super series it was worse that the guy ripped his arm off...) Captain Ginyu was Frieza's strongest man and he only had a power level of 120k. Frieza was at 530k in his first form, over 1 million in his second form. It was said his full power was at 120 million... 1000 times stronger than Captain Ginyu.
I think it is actually quite sad that the author try to make everyone else useless to in order to give Goku the spotlight. By doing so, the logic failed on so many levels. They even went as far as letting Master Roshi to fight, but Yamcha was nowhere to be found who should be at least 1000 times stronger than Roshi at that point. Made Buu "sleeping" is another attempt to give Goku the spotlight. Gotenks showed up but timed out and de-fused right away in front of Frieza (in Super) was also ridiculous.
In the old Z series, number also does not matter. As a single strong character far above everyone else could use a single large attack to wipe out everyone along with the planet if he/she wishes. Yet, all those small fish Frieza brought were giving the Z fighters some troubles. Even if all of them were on the bar of Zaborn and Dodoria (impossible... more like in the range of 1,000~3,000 at most), the human fighters alone could have beat them all. Piccolo should have been able to blow them all away with a single cough.