YES ----adding a fan to improve draft across cooling unit can help.
With a roof vent (vs sidewall vent due to install in slideout)and PROPER Installation by RV MFG a fan should NOT be necessary.
Natural draft airflow S/B sufficient IF----BIG IF---installation clearance requirements were met, baffling was used if needed, cabinet fridge installed in properly sealed/insulated and dead air spaces eliminated.
So YES..fan will help increase air flow....but if clearances, sealing, dead air space still are an issue the fan will NOT help very much
By '4 door Dometic' I assume you mean a RM1350 Model??
If so.....check out pages 33/34 for Installation Requirements and check IF your fridge was installed correctly.
RM1350 Service Manual
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31