In short, yes it was. If you agree with Adrian Goldsworthy's view put forward in his "Fall of the West" the 3rd Century Crisis the catalyst for the fall of the united Roman Empire. Before the Crisis, Rome had been through the Pax Romana, about 200 years of peace around the Mediterranean basin unrevealed at any other point in history before or after. There were civil wars during this period, the Year of the 4 Emperors being the most famous as well as small scale rebellions such as Cassius's rebellion against Marcus Aurelius but on the whole the first two centuries were once of peace in the Roman Empire. That started to change with the civil war's after the death of Pertinax and at the beginning of Septimius Severus's reign which were far more destructive than the Year of the 4 Emperors but still ended with just over 40 years of peace between 193 and 235 under the Severan Dynasty, however with the death of Alexander Severus in 235, the Empire descended in to a period of military anarchy. In 238 there were 6 emperors proclaimed, Maximinus Thrax, Gordian I, Gordian II, Gordian III, Pupienus and Balbinus. Between this year and in the ensuing half century there were 26 claimants to the Imperial Throne. Emperors at this time who did have significant reigns like Gallienus spent most of their time fighting other usurpers. This had the knock on effect of eroding the strength of the army, and weakening the economy partly due to the Emperor's debasing the currency to pay for their civil wars. There were also huge Germanic invasions of the Empire during this period, such as the Gothic raids in the Black and Aegean seas and the Alamannic invasions of Italy which reached Rome itself. Perhaps the most poignant image of the crisis is the fact that for the first time ever an Emperor was killed in battle against Germanic tribes, Decius, and an Emperor was captured by the Persians for the first time (Valerian). To top this off, by 271 the Empire had split in to 3 functionally separate Empires (the "legitimate" one based around Rome, the Gallic Empire with its capital at Trier and the Palmaryene Empire of Zenobia based in Syria) which were reunited by Aurelian by 275. Oh and there were also successive bouts of the Antonine Plague as well. The Crisis only started to end with Aurelian's rule in the 270s when the Empire was reunited in to one, but sustainable peace was only established with Diocletian who's reign began in 284.

Compared to the second century Rome emerged significantly weakened. The Imperial Army had spent most of those 50 years fighting itself leading to an inevitable decline in effectiveness. The Emperor himself became increasingly isolated from rule with an expansion of the bureaucracy under Diocletian and later Constantine and trade & prosperity, especially in the west declined significantly.

As I mentioned before, there is some debate as to how far the Crisis weakened the empire with some academics claiming that the Empire of the 4th century was as strong as that of the second while others (lead by Mr Goldsworhy) say that the Crisis marked a point from which Rome could never regain its former prosperity and power.