No, BLU doesn't get Fast Cast I from having one tier. The Gift brings it to normal FC1.
Bonus maths, here's some numbers for various DW stuff with DW5:
Capped Gear Haste + Haste II + DW5
256/1024 + 300/1024 + 35% DW
1 - .35 = .65
1024 - 256 - 300 = 468
468 * .65 = 304
304/1024 = 29.7% Delay Remaining, 70.3% Delay Reduction
Capped Gear Haste + Haste II + DW5 + Suppa
256/1024 + 300/1024 + 40% DW
1 - .4 = .6
1024 - 256 - 300 = 468
468 * .6 = 280
280/1024 = 27.3% Delay Remaining, 72.7% Delay Reduction
Capped Gear Haste + Haste II + DW5 + Suppa + Taeon Boots
256/1024 + 300/1024 + 44% DW
1 - .44 = .56
1024 - 256 - 300 = 468
468 * .56 = 262
262/1024 = 25.6% Delay Remaining, 74.4% Delay Reduction
Capped Gear Haste + Haste II + DW5 + DWEarSet + Taeon Boots
256/1024 + 300/1024 + 46% DW
1 - .46 = .54
1024 - 256 - 300 = 468
468 * .54 = 252
252/1024 = 24.6% Delay Remaining, 75.4% Delay Reduction
Capped Gear Haste + Haste II + DW5 + DWEarSet + Taeon Boots + Shetal Stone
256/1024 + 300/1024 + 52% DW
1 - .52 = .48
1024 - 256 - 300 = 468
468 * .48 = 224
224/1024 = 21.9% Delay Remaining, 78.1% Delay Reduction
Capped Gear Haste + Haste II + DW5 + DWEarSet + Taeon Boots + Shetal Stone + Thurandaut Head or Haverton Ring
256/1024 + 300/1024 + 57% DW
1 - .57 = .43
1024 - 256 - 300 = 468
468 * .43 = 201
201/1024 = 19.6% Delay Remaining, 80.4% Delay Reduction
Capped Gear Haste + Haste II + March + DW5
256/1024 + 448/1024 + 35% DW
1 - .35 = .65
1024 - 256 - 448 = 320
320 * .65 = 208
208/1024 = 20.3% Delay Remaining, 79.7% Delay Reduction