Egwene did not Heal Gawyn. She performed Healing weaves on him, but they were essentially ineffective. Her solution wasn't to grab an angreal and try to heal him it was to find a woman with more Talent to do the job. No amount of extra power was going to save Gawyn. This isn't too different from when Sorilea was able to make the gateway weave, but could not make it work. Unlike Androl, she doesn't have a strong enough Talent to make the weave function enough to be useful. Nor does Egwene have enough Talent to be an effective Healer.

Siuan is an average healer ... She managed to save Brynes soldiers which is significantly more than Sheriam, Egwene or Elayne can manage. The FACT that her ability to Heal changed not at all is because Talent doesn't change, it just is what it is. The Talent defines how much Power is necessary to make the weaves work, but no amount of additional power will let you have a greater effect than your Talent allows. S if you get a greater effect when you have an angreal it follows that your Talent is strong enough to continue to let you have an increased effect.

Flinn is one of the stronger Asha'man and openly states he has difficulty with Traveling. Androl can make a gateway large enou for a WAGON ... Androl makes gateways like Rands! Flinn has a weaker Talent for Traveling and therefor struggles with the weave despite being able to add power to it. His comment makes it clear that based on his strength he thinks he should be able to make one larger.

Rand may well be an exception now that he is "super Rand" ... After what he did at Maradon I won't rule anything out.

Every single Talent we have seen so far has shown us degrees of ability ... There are no "abstract" Talents. Like every other Talent, Foretelling or Dreaming or Ter'angreal ability, if the Talent is there an individual will have a set amount of ability with it. For all we know Nynaeve and Aviendha have the same Talent as Elayne, but to different degrees. Nynaeve gets "feelings" Aviendha can sense "purpose" and Elayne seems to be able to sense "form" therefore she can reproduce them to a degree. Certainly the Talents that require no weaves operate differently, but it doesn't change that Elaida had a weak FT Talent and Nicola a strong FT Talent.

I would say every Talent we have seen that requires specific weaves are incredibly common Talents, but the variation in the Talent defines how well the weave is executed. Thus you have wildly swinging variations on the Healing Talent that doesn't seem to have any correlation to OP Strength. Traveling looks to be the same ... Else why bother showing Androl or tell us Flinn can't make a gateway as large as his OP strength says he should? There is now proof that the ability to Travel is not dependent on OP strength, the stronger the Talent the weaker the Channeler can be and still pull off the weave. Clearly an individual with "average" Talent needs to dedicate a certain amount of OP into the weave to give it enough juice to function, but that isn't surprising ... We've seen plenty of weaves that require a lot of power to operate. But assuming how large a gateway is will give you even a general sense of a Channelers strength is a mistake as a very strong Channeler may only be able to create a small personal gateway if they have a weak Talent. And like everything else in WoT this is probably on the rare side. Outliers like Androl are obviously very rare, but what about someone like Beonin? IIRC she was able to create a quite large gateway... Much larger than she should have been able too ... Very easy to think she may have a disproportionate Talent for her strength. Sort of like Samitsu being "as effective as a circle" with Healing.

The WF have essentially inbred for 3000+ years and have become highly specialized in both knowledge and in genetic abilities. Over time they would have bred the Talent as well as the flow affinity into almost every woman. And please note it was the strength obsessed AS who made the call on the strongest women. It's clear that most Channelers from the modern era have not really pieced together that strength doesn't make much difference with Talents ... If they knew that they may have stepped back and given only WF a place in the use of the Bowl. Just like they did in the AoL ... Choose people for a circle based on their abilities rather than on strength.