When I attempted that mission, at first I also failed miserably mostly because I wasn't expecting the amount of units that are thrown at Tiki and I had positioned my units on the Forests surrounding the central area. While I manage to take out a great number of enemy units, eventually they came faster than I could take them out and they swarmed Tiki.
Afterwards I just 300dred around Tiki, leaving a space between the formation and herself to avoid those 1-2 range units and it was rather easy.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
