I feel like Haggar doesn’t have the right tools to follow up a successful tatsu or to mix up the opponent to let the tatsu hit/cover him. If anything it can nullify projectiles while you wavedash up and try for a hoodlum M but that seems gimmicky and telegraphed as well. If you call him you should be wavedashing/jumping along with him to follow up at a closer range if it connects, probably either pipe or a jump loop off the last hit of the tatsu if you’re close or try to catch with Hoodlum L if you can’t reach quite fast enough.
Have you tried changing team order so that Akuma is 2nd and Haggar is 3rd? The pros to this is that you have Akuma who is more mobile and may have more use of a ‘get off me’ assist that gives a hard knockdown, as Akuma has plenty of OTG options. Coming in at 2nd, Akuma should have a lot of meter to work with if your Dante can pull off his combos. So in a way your Akuma would sort of play like your Dante presumably does, rushing in with teleport/aerial mixups while calling Haggar for the hard knockdown to get things going OTG.
The downside to this order would be that you run the risk of losing XF3 Akuma, who can make comebacks as an anchor on his own sometimes… Haggar has a much more difficult time doing this. You could maybe keep Haggar in 2nd and just sniff out an air grab or some other hard knockdown to OTG body press DHC beam super maybe and vice versa once Akuma is in to get some easy damage/burn some meter.
I don’t play Akuma and Haggar on the same team but hopefully those are some good ideas to get you started. IIRC Duey (of WNF fame) plays an alternate team of Haggar point, Akuma tatsu then Sent drones… And he also plays Dante/Haggar if you need some ideas with that.