We use Deviance Information Criterion (DIC) and the posterior mean of the total residual deviance to assess Bayesian model fit. how to assess the frequentist model fit under network meta-analysis?
Under frequentist framework, the akaiki information criterion (AIC) is the alternative choice. I advise to read this book which gives you the criteria used either in case of Bayesian or frequentist situations.
Biondi-Zoccai G (2014) Network Meta-Analysis: Evidence Synthesis with Mixed Treatment Comparison. Hauppauge, NY: Nova Science Publishers.
DIC is a model comparison/selection criterion and not a goodness-of-fit criterion. There are frequentist analogues such as the AIC as Safaa suggested.
For model fit, perhaps you refer to deviance residuals. Deviance and deviance residuals are not limited to a Bayesian framework. You may have them on a frequentist framework as well, in which you would get point estimates instead of a posterior distribution (and possibly its mean)
In my opinion, it is more important to focus on (in)consistency, which is a fundamental assumption of the NMA model, and heterogeneity rather than DIC and deviance