I could make some and test, but I have yet to find a single Engineering item that is usable. I am aware that the rocket launcher is, but that is Goblin only. Ironically the Gnomish counterpart (chicken ray) is *not* usable.
As an engineer myself i'd be very keen ot know if there is a definitive list of what does and does not work in arenas. So i've heard (but am yet to try) that the following work as per posts above:
- rocket launcher
- nigh invulnerability belt
- rocket boots
But what about a whole host of other things like recombulators, shadow/fire/frost reflectors, rocket helms, mind control helm etc? It occurs to me that the reflectors (especially shadow) could be superb in arenas. I'll do some tests myself if no body knows but if anyone does know a place where this information can be found that would be good.
Reflectors work but have a huge failure rate vs. 70s (IIRC they nerfed them the same time as tidal charm nerf). I'd love an upgraded schematic that works on 70s and takes the appropriate primals and such to make.
Reflectors work in arenas, but there is a high chance that they will fail. It will either work for the entire duration or not at all - you get something along the lines of 'you resist your shadow reflector' if it fails, otherwise you get the reflect buff.
Reflectors work, the fail rate is really not that bad at all, nowhere near something like the net projector anyway. Belt works as well, this thing has a bad fail rate though, failure is horrible too you're guaranteed to die if it fails. Rocket and MC helmets have 30 min cd, no arenas. Bad fail rates at 70 anyway. I'd say reflectors are worth the slot, especially shadow at higher and fire at lower rated 2s - hey I've seen people use the soulstone trinket; belt would've been worth it in 5s if it wasn't for the failures. Rocket launcher? I'm not real sure of usefulness, I was gnome so I never had one, looks awesome as hell though.