Every introduction is different. Some go smoothly and birds can be together faster (after quarantine of course). Some introductions take longer. I think my best introduction was in one afternoon and I was comfortable leaving everyone together unattended without a divider. I think my worst one was 6-8 weeks of see no touch, then limited interaction with certain combinations, then eventually everyone together all the time. I like to set up a see no touch divider or something. Then watch them. Once it gets to a point where they ignore the ducks on the other side of the barrier consistently, it is generally safe to remove the barrier. Trust me, you will know if it's going poorly. I've had birds trying to attack each other through the fencing, pacing, making noise, charging, banging on the bars/fence (these are all signs that they shouldn't be together yet!). Peacefully acting the same as normal is the goal, being quiet, eating, drinking, preening, etc. Once this is the norm, they can all mingle. Once you merge them, continue to give at least two feeders and two waterers, it will give everyone options and no one can be bullied out of eating/drinking.
If Tina only gets one female to be with the drake it may or may not work out. She may get over-mated and kinda beat up, but he will likely be lonely if he is the only duck, so I think it's worth trying.