I removed the emb_dim and changed to the 300d pretrained word embeddings.
INPUT_DIM = 20002
HID_DIM = 300
OUT_DIM = 1
N_LAYERS = 4
N_HEADS = 6
FF_DIM = HID_DIM * 2
MAXLEN = 100
Epoch: 01 | Epoch Time: 1m 15s
Train Loss: 0.554 | Train Acc: 71.35%
Val. Loss: 0.467 |  Val. Acc: 77.56%
Epoch: 02 | Epoch Time: 1m 15s
Train Loss: 0.402 | Train Acc: 81.82%
Val. Loss: 0.457 |  Val. Acc: 79.22%
Epoch: 03 | Epoch Time: 1m 15s
Train Loss: 0.359 | Train Acc: 84.33%
Val. Loss: 0.526 |  Val. Acc: 74.28%
training results from old config (with transformerblocks)
INPUT_DIM = 20002
HID_DIM = 300
OUT_DIM = 1
N_LAYERS = 2
N_HEADS = 2
FF_DIM = 128
MAXLEN = 100
Epoch: 01 | Epoch Time: 0m 30s
Train Loss: 0.464 | Train Acc: 77.80%
Val. Loss: 0.421 |  Val. Acc: 81.38%
Epoch: 02 | Epoch Time: 0m 30s
Train Loss: 0.314 | Train Acc: 86.78%
Val. Loss: 0.442 |  Val. Acc: 80.23%
Epoch: 03 | Epoch Time: 0m 30s
Train Loss: 0.227 | Train Acc: 91.24%
Val. Loss: 0.524 |  Val. Acc: 79.14%
Epoch: 04 | Epoch Time: 0m 30s
Train Loss: 0.159 | Train Acc: 94.36%
Val. Loss: 0.643 |  Val. Acc: 77.77%
Epoch: 05 | Epoch Time: 0m 30s
Train Loss: 0.118 | Train Acc: 95.82%
Val. Loss: 0.622 |  Val. Acc: 78.18%
training results from old config (without transformerblocks)
Epoch: 01 | Epoch Time: 0m 4s
Train Loss: 0.607 | Train Acc: 69.78%
Val. Loss: 0.521 |  Val. Acc: 76.43%
Epoch: 02 | Epoch Time: 0m 4s
Train Loss: 0.428 | Train Acc: 81.96%
Val. Loss: 0.432 |  Val. Acc: 80.48%
Epoch: 03 | Epoch Time: 0m 4s
Train Loss: 0.343 | Train Acc: 85.94%
Val. Loss: 0.409 |  Val. Acc: 81.34%
Epoch: 04 | Epoch Time: 0m 4s
Train Loss: 0.292 | Train Acc: 88.55%
Val. Loss: 0.417 |  Val. Acc: 80.56%
Epoch: 05 | Epoch Time: 0m 4s
Train Loss: 0.255 | Train Acc: 90.13%
Val. Loss: 0.412 |  Val. Acc: 81.23%