Honestly the pairing is nowhere near as bad as you'd think, 104.7 Drtg. Best of Kemba paired with any major rotation player (may be slightly skewed by not including the early days when Kemba was awful coming back from injury). The 118.5 Ortg is the best of any Kemba pairing.
For Fournier, the Kemba pairing is his 2nd best significant minute offensive pairing (behind TL) and 4th best defensive pairing (TL, Kornet, Grant).
Going forward that's a very reasonable backcourt.
Adding Tatum it's one of his stronger 3 man groupings,
The 4 man unit with Brown has barely played due to injury, but the bit it did it was very good.
I have no real concerns about the Kemba/Fournier pairing going forward, it's not that bad defensively and it's very good offensively, given what we have in terms of Brown, Tatum, TL I think that's a strong lineup.... TT probably would need to be replaced with more of a mobile rim-protector as the backup C.