Wireless Sensor Networks (WSNs) are instrumental facilitators in the development of the Internet of Things (IoT). In the smart world of IoT, energy efficient data gathering is an essential requirement to extend the sustainability of the network. In WSNs, Data Aggregation Trees (DATs) are employed for energy efficient data gathering. While DAT gathers data, it is imperative that the network provides enhanced Quality of Service (QoS). Constructing a DAT that caters to the requirements of the application results in improved QoS. This work explores QoS of DATs with Network Lifetime (NL) as a parameter for QoS. QDD, an algorithm to enhance QoS of DATs with Deterministic Network Model(DNM) is proposed. In DNM, any two sensors either communicate or they do not. However, in practical scenarios the communication between a pair of sensors is probabilistic and is represented using the Probabilistic Network Model (PNM). QDP, an algorithm to enhance QoS of DATs with PNM is proposed. Simulation results show the effectiveness of the proposed algorithms and demonstrates improved QoS through DAT path refinements.