Deterministic Synchronous Multichannel Extension (DSME) and Time Slotted Channel Hopping (TSCH) are two emerging MAC behaviors that are based on IEEE 802.15.4 and permit the deployment of wireless sensor devices in a variety of Industrial Internet of Things (IIoT) environments. While TSCH focuses on multi-channel hopping and fixed-size TDMA timeslots, DSME primarily addresses the drawbacks of the legacy IEEE 802.15.4 MAC, including the best use of the Guaranteed Time Slots (GTSs) and the application of channel diversity techniques. However, the existing literature lack the robustness for an ideal IIoT setup. In this regard, our suggested i-DSME MAC offers the best Quality of Service (QoS), incorporating an effective sensor prioritization strategy and suitable channel assessment techniques. The associated QoS constraints of the sensor devices are also considered by i-DSME in its core methodology, which is not explored adequately in the existing literature. To demonstrate the compatibility of i-DSME’s adaptability with the body of existing literature, we run thorough simulations of it. The results demonstrate that, on average, the proposed MAC protocol is more efficient than the benchmarks in terms of goodput (>39.82%), reliability (>12.50%), packet drop rate (>19.69%), and delay (>54.37%).