Overview
Gr MG5 is an MG that deals increased Damage with every 4th attack. Her SPEQ makes this attack “Surecrit”, and her SPEQ-set adds some random bonuses.
Gr MG5 still has most of the regular MG issues (reloading, random targeting), though Accuracy is somewhat alleviated with the SPEQ. While the two offensive bonuses (50% DMG and 50% CRate) from her SPEQ-set are very strong, even if these had a 100% uptime MG5 would still be outclassed by better MGs. The fact that you have 3 defensive "buffs" also in the same pool just makes it disappointing. On average, the SPEQ itself is better than the actual Set effect.
While both SPEQs are certainly very good, the set is mediocre and overall there are far better MGs available these days. As such, MG5 is not recommended to be raised.
Note that some older guides will call Terminating Barrage MGs the “Big 4”. They may have been some of the better MGs at some point in the past, but this does not mean they have kept up with new enemies, Dolls and Mods being added. Again, Gr MG5 is not recommended for general use.