Circuit? Layout?
Mind that you may see dead time disappear at high duty%, because it all kind of mashes together. Example (from a TL598 and transformer):
The GDT + load is a lowpass filter, L = leakage inductance, R = ESR, C = Cg(eff), which rolls off the corners of the waveform, and hopefully nothing more than that. Trifilar helps a lot (it makes the leakage quite predictable), but it doesn't minimize it -- this is okay for smaller applications, but you may find you need a much lower impedance, to drive heavy gates fast enough (or to reduce switching time to raise efficiency), in which case you need to use multiple trifilar windings in parallel.
(What you're ultimately doing: this type of construction is called a transmission line transformer. The impedance of the transmission line used, corresponds to the impedance where the transformer has its maximum bandwidth -- that is, its high frequency limit, corresponding to the electrical length of the winding. If the wire length is about a meter, expect on the order of 50MHz cutoff, at the characteristic impedance of the line. The impedance of trifilar is probably around 100 ohms. If used at different impedances -- gate drives are usually quite a bit lower, maybe 50-10 ohms -- then the high frequency limit is that many times lower, and that's where the filtering comes from. You can get the bandwidth back by wiring transmission lines in parallel. Which does necessarily increase the isolation capacitance in the transformer, which is actually good in one (limited) sense, but, generally worse overall. Note that, whatever way you build the transmission lines, they all need the same number of turns around a core, which can be a common core, so you get the same magnetizing inductance (and LF cutoff) as you have now.)
Tim